Water Resources Working Group Report

This report provided content for the Wisconsin Initiative on Climate Change Impacts first report,

Wisconsin’s Changing Climate: Impacts and Adaptation, released in February 2011.

Water Resources Working Group Wisconsin Initiative on Climate Change Impacts

October 2010

Water Resources Working Group Members – WICCI

Tim Asplund (Co-Chair) - Wisconsin Department of Natural Resources James Hurley (Co-Chair) - University of Wisconsin Sea Grant & University of Wisconsin Water Resources Institute Tom Bernthal - Wisconsin Department of Natural Resources Carolyn Betz - University of Wisconsin-Madison Ken Bradbury - University of Wisconsin-Extension Wisconsin Geological and Natural History Survey Esteban Chiriboga - Great Lakes Indian Fish and Wildlife Commission Alison Coulson – University of Wisconsin-Madison and Wisconsin Department of Natural Resources Andy Fayram – Wisconsin Department of Natural Resources Steve Elmore – Department of Natural Resources Paul Garrison – Wisconsin Department of Natural Resources Steve Greb – Wisconsin Department of Natural Resources Tim Grundl – University of Wisconsin-Milwaukee Bob Hansis – Wisconsin Department of Natural Resources Jen Hauxwell – Wisconsin Department of Natural Resources Dale Higgins – U.S. Forest Service Randy Hunt – U.S. Geological Survey George Kraft – University of Wisconsin-Stevens Point Richard Lathrop – Wisconsin Department of Natural Resources and University of Wisconsin-Madison Steve Loheide – University of Wisconsin-Madison John Magnuson – University of Wisconsin-Madison Mike Miller – Wisconsin Department of Natural Resources Erin O'Brien – Wisconsin Wetlands Association Ken Potter – University of Wisconsin-Madison Dale Robertson - U.S. Geological Survey Steve Westenbroek - U.S. Geological Survey

Report Preparation

Primary Authors Carolyn Rumery Betz Tim Asplund James Hurley

WICCI Science Council Reviewers Sharon Dunwoody

Barry Johnson

John Kutzbach

Internal Working Group Reviewers Jen Hauxwell Dale Higgins Cover Photo Credits: Wolf River, Richard Betz; Lake Mendota, Lake Michigan, Wisconsin River: Carolyn Betz Spring Green Flooding, 2008, FEMA

Contributors Tom Bernthal

Alison Coulson

Eric Erdmann

Paul Garrison

Steve Greb

Bob Hansis

Dale Higgins Randy Hunt Paul Juckem Erin O’Brien Dale Robertson

Christina Wolbers

TABLE OF CONTENTS EXECUTIVE SUMMARY . .............................................................................................................................. ii

CHAPTER I. DESCRIPTION OF THE WATER RESOURCES WORKING GROUP ...................................................................... 1 Working Group Charter and Participants ...................................................................................................................... 1

Identifying Research Gaps ............................................................................................................................................. 3

Process to Identify Climate Change Impacts and Adaptations ...................................................................................... 4

Ongoing Activities and Future Plans .............................................................................................................................. 5

CHAPTER II. WISCONSIN’S WATER RESOURCES ............................................................................................................................. 7

CHAPTER III. HISTORIC TRENDS IN WATER RESOURCES IN WISCONSIN ........................................................................ 11 Ice Cover Data .............................................................................................................................................................. 11

Water Levels ................................................................................................................................................................ 14

Lakes ........................................................................................................................................................................ 14

Case Study − Silver Lake, Barron County ............................................................................................................ 18

Case Study – Berry Lake, Shawano County ......................................................................................................... 20

Case Study − Max Lake, Vilas County ................................................................................................................. 21

Groundwater Levels ................................................................................................................................................ 22

Historic Trends in Flows of Wisconsin Rivers and Streams.......................................................................................... 23

Comparing the Past with the Projected Future ........................................................................................................... 24

Trends in Wetlands – Loss of Wetlands Over Time ..................................................................................................... 25

Water Resources Trends Analysis ................................................................................................................................ 26

CHAPTER IV. CLIMATE ASSUMPTIONS, DRIVERS AND UNCERTAINTIES ......................................................................... 27 Climate Drivers ............................................................................................................................................................ 28

Uncertainties ............................................................................................................................................................... 28

U.S. Geological Survey: Studies of Climate Change on a Watershed Scale........................................................ 30

CHAPTER V. PROJECTED IMPACTS OF CLIMATE CHANGE........................................................................................................ 30 PROJECTED IMPACTS ................................................................................................................................................... 32

HYDROLOGIC PROCESSES ............................................................................................................................................ 32

Impacts on the Built World .......................................................................................................................................... 33

Lakes ............................................................................................................................................................................ 33

Increased sediment and nutrient loads ................................................................................................................... 33

Case Study – Lake Mendota ................................................................................................................................ 34

Aquatic Invasive Species .......................................................................................................................................... 34

Species and Habitat Shifts ....................................................................................................................................... 34

Changes in Ice Cover ............................................................................................................................................... 35

Physical Impacts ...................................................................................................................................................... 35

Changing Lake Levels ............................................................................................................................................... 35

Rivers and Streams ...................................................................................................................................................... 37

Baseflow .................................................................................................................................................................. 37

Rainfall and Runoff .................................................................................................................................................. 37

Fish Habitat ............................................................................................................................................................. 38

The Built Environment ............................................................................................................................................. 38

Groundwater ............................................................................................................................................................... 38

Groundwater Recharge ........................................................................................................................................... 39

Case Study on Groundwater Flooding ................................................................................................................ 39

Thermal Impacts on Groundwater .......................................................................................................................... 40

Groundwater Quality............................................................................................................................................... 41

Wetlands ...................................................................................................................................................................... 41

Changes in Hydrology .............................................................................................................................................. 42

Increased Sediment and Nutrient Loads ................................................................................................................. 42

Proliferation of Invasive Species: ............................................................................................................................ 43

Shifts in Plant, Aquatic and Animal Communities ................................................................................................... 43

Great Lakes Coastal Wetlands ................................................................................................................................. 44

CHAPTER VI. INFORMATION GAPS – RESEARCH, INVENTORY AND MONITORING NEEDS ...................................... 47 Monitoring and Inventory Needs ................................................................................................................................ 47

Research Needs ........................................................................................................................................................... 49

Groundwater Research and Monitoring Program ................................................................................................... 50

UW-WRI Climate Impacts Solicitation ..................................................................................................................... 51

Funded Projects ....................................................................................................................................................... 51

Ongoing and Current Research ............................................................................................................................... 51

CHAPTER VII. ADAPTATION STRATEGIES FOR WATER RESOURCES .................................................................................. 53 Goals of Adaptation for Water Resources ................................................................................................................... 53

Other Adaptation Concepts ......................................................................................................................................... 54

Impacts and Adaptation Strategies ............................................................................................................................. 55

REFERENCES CITED .................................................................................................................................................................................... 59

APPENDIX A. WATER RESOURCES WORKING GROUP CHARTER .......................................................................................... 62

APPENDIX B. HISTORIC TRENDS IN FLOWS OF WISCONSIN’S RIVERS AND STREAMS .............................................. 64

TABLE OF FIGURES

Figure 1. Wisconsin’s water resources. . ....................................................................................................................... ii

Figure 2. River baseflow trends ..................................................................................................................................... v

Figure 3. Groundwater flooding near Spring Green .................................................................................................... vii

Figure 4. Flow diagram of the Water Resources Working Group .................................................................................. 2

Figure 5. 2008 Wisconsin Wetlands Association meeting photo .................................................................................. 4

Figure 6. Wisconsin’s hydrologic cycle .......................................................................................................................... 7

Figure 7. Wisconsin’s 12 wetlands types. ..................................................................................................................... 9

Figure 8. 150 years of ice cover data and map ........................................................................................................... 12

Figure 9. Annual ice duration for three lakes in Wisconsin. ........................................................................................ 13

Figure 10. Ice duration of Lake Mendota ................................................................................................................... 14

Figure 11. Map for locations of lake levels and groundwater levels ........................................................................... 15

Figure 12. Annual water levels for three lakes in Wisconsin. ...................................................................................... 16

Figure 13. Water levels of Anvil Lake ........................................................................................................................... 17

Figure 14. Trophic state index (TSI) values for Silver Lake, Barron County. ................................................................ 19

Figure 15. Berry Lake level .......................................................................................................................................... 20

Figure 16.Hydrologic connectedness of lakes ............................................................................................................. 22

Figure 17. Lake hydrology and position in the landscape ............................................................................................ 22

Figure 18. Groundwater levels for three wells ........................................................................................................... 22

Figure 19. Annual stream and river baseflows. .......................................................................................................... 23

Figure 20. Climatic sections for Wisconsin ................................................................................................................. 24

Figure 21. Historical data vs. average return period .................................................................................................. 25

Figure 22. Localized flooding ....................................................................................................................................... 29

Figure 23. Basin mean values of evaporation and basin soil water ………………………………………………………………………..30

Figure 24 Contrasting high and low lake levels ........................................................................................................... 36

Figure 25. Groundwater flooding in Spring Green....................................................................................................... 40

Figure 26. A coastal wetland ....................................................................................................................................... 44

EXECUTIVE SUMMARY Wisconsin’s water resources are an important part of what defines us as a state and as a people. The

Mississippi River, Lake Superior and Lake Michigan help define our borders, and the 84,000 miles of

streams, 15,000 lakes, 5.3 million acres of wetlands, and plentiful, though finite, supply of groundwater

support industrial and agricultural activities and enrich our recreational opportunities (Figure 1).

Wisconsin’s climate is changing (Kuckarik et al., 2010), and our water resources are changing, too. Many

aspects of our water resources respond to climate and can serve as indicators of climate change at

various temporal and spatial scales. Analysis of historical data shows that water resources are intimately

linked to local and regional climate conditions. Long-term records of lake water levels, lake ice duration,

groundwater levels, and stream baseflow are correlated with long-term trends in atmospheric

temperature and precipitation.

We anticipate that future climate projections will affect our state’s water resources in both quantity and

quality. Our working group cautions, however, that there may be different hydrological responses to

climate change in different geographic regions of the state. This is clearly evident in analysis of past

trends in Wisconsin and probable future climate projections. The differences reflect variations in land

use, soil type and surface deposits, groundwater characteristics, and runoff and seepage responses to

precipitation.

GOALS OF ADAPTATION STRATEGY The Water Resources Working Group (WRWG) includes 25 members representing the federal

government, state government, the UW System, the Great Lakes Indian Fish and Wildlife Commission,

and the Wisconsin Wetlands Association. Members are considered experts in the fields of aquatic

biology, hydrology, hydrogeology, limnology, engineering, and wetland ecology in Wisconsin. Over the

course of a year, the group convened to discuss current climate-related water resources research,

potential climate change impacts, possible adaptation strategies, and future research and monitoring

needs. We also hosted several workshops to solicit ideas from other professionals, garnering additional

information and ideas.

This report serves as the first assessment of the impacts of climate change on our water resources and

outlines preliminary strategies to adapt to projected changes. As we gain a better understanding of the

downscaled climate data specific to Wisconsin, future reports will further refine how we expect our

water resources to change and how we can be proactive in preparing for those changes at statewide

and local levels.

The goals of developing water resource adaptation strategies to climate change dovetail well with on-

going priorities and concepts that guide our water resource management programs in Wisconsin.

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Figure 1. Wisconsin’s vast water resources are a vital part of our state (Map prepared by Kate Barrett, DNR, 2010).

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Climate change may compel managers to emphasize and prioritize these issues, and perhaps will be

used to leverage additional resources to implement the needed strategies. The goals are as follows:

Minimize threats to public health and safety by anticipating and managing for extreme events--floods and droughts We cannot know when and where the next flooding event will occur or be able to forecast drought

conditions beyond a few months, but we do know that these extreme events may become more

frequent in Wisconsin in the face of climate change. More effective planning and preparing for

extreme events are an adaptation priority.

Increase resiliency of aquatic ecosystems to buffer the impacts of future climate changes by restoring or simulating natural processes, ensuring adequate habitat availability, and limiting human impacts on resources A more extreme and variable climate (both temperature and precipitation) may mean a shift in how

we manage aquatic ecosystems. We need to try to adapt to the changes rather than try to resist

them. Examples include managing water levels to mimic pre-development conditions at dams and

other water level structures, limiting groundwater and surface water withdrawals, restoring or

reconnecting floodplains and wetlands, and maintaining or providing migration corridors for fish and

other aquatic organisms.

Stabilize future variations in water quantity and availability by managing water as an integrated resource, keeping water “local” and supporting sustainable and efficient water use Many of our water management decisions are made under separate rules, statutory authorities,

administrative frameworks, and even different government entities. This can lead to conflicting and

inconsistent outcomes. In the face of climate change, the more we can do to integrate these

decisions at the appropriate geographic scale, the better adapted and ready for change we will be.

In addition, treating our water as a finite resource and knowing that supply will not always match

demand will allow for more sustainable water use in the future.

Maintain, improve, or restore water quality under a changing climate regime by promoting actions to reduce nutrient and sediment loading Water quality initiatives will need to be redoubled under a changing climate in order to minimize

worse-case scenarios such as fish kills, harmful blue-green algae blooms, or mobilization of

sediments and nutrients and to prevent exacerbation of existing problems.

ASSUMPTIONS, CLIMATE DRIVERS, AND UNCERTAINTIES We reviewed and incorporated into our assessment the WICCI Climate Working Group’s projections for

temperature, precipitation (including occurrence of events), and changes in snowfall in multiple

locations in the state for 1980-2055. The WRWG used the following projections to guide our evaluation

of potential impacts to hydrologic processes and resources.

Thermal impacts will include increased air and water temperatures, longer ice-free periods, and more evaporation and transpiration.

Changing rainfall patterns will include seasonal and spatial variability, less precipitation in the form of snow, and more water in some parts of the state but less in other parts.

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Storm intensities will increase, with slightly more frequent events of greater than two inches of precipitation in a 24-hour period.

Climate drivers are those factors that may cause change or impact the resource. The main drivers we

identified are large rainfall events, water availability, or warming temperatures.

Large rainfall events are thought of as frequent rainstorms, rainstorms that are high in intensity,

and rain that falls over a long duration and/or at times of the year when resources are most

vulnerable to change.

Water availability could be either positive (too much)—such as flooding, or negative (too

little)—such as a drought. Too much or too little precipitation can affect water resources. These

changes, as shown in the WICCI climate change maps, vary across the state. The seasonal

variation in temperature will also affect the form of precipitation, particularly through less

snow.

Increase in temperature includes both air and water temperatures, longer ice-free periods in the

winter, and an increase in evapotranspiration (ET).

The role of evapotranspiration and its effect on the water budget has been identified as one of our

group’s key research needs in climate projections. However, we are using the assumption of the Climate

Change Working Group that ET will increase in most locations in the state because of the warmer

conditions, but how that will affect water resources is not clear. Increased ET may override increases in

precipitation, negating potential changes in lake levels.

HISTORIC ANALYSIS Our group recognizes the strong relationships between past trends in climate and hydrologic responses.

Robust data sets of ice cover indicate that since the 1850s, average ice cover has decreased between 10

and 40 days, with greater effects in southern lakes, such as Lake Mendota, where the period of ice cover

has declined 19 days per century (Magnuson, et al., 2003).

Lake level responses are not spatially consistent statewide according to limited U.S. Geological Survey

data sets. In the north central part of the state, water levels of many lakes have gradually decreased

and are currently at the lowest levels in the 70-year record. In the central part of the state, water levels

have been variable and are currently low, but not as low as in the 1930s and 1960s. In the southern part

of the state, water levels appear to have increased since the 1960s but parallel historic climate change

statewide. Groundwater levels have responded similarly.

The WRWG also reviewed the recent Wisconsin DNR analyses of stream flow characteristics in

Wisconsin streams for the period similar to the analysis window of Kucharik et al. (2010). The analysis

revealed mean annual flow increasing overall statewide by about 14 percent over the past 56 years,

which is consistent with Kucharik et al. (2010) and their reported 10-15 percent increase in precipitation

over the same period (Figure 2). Similar to the lake level and groundwater monitoring wells, decreases

in annual flow were only observed in north central Wisconsin.

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IMPACTS OF CLIMATE CHANGE We expect that there will be system-wide changes in hydrologic patterns that may not be completely

predictable. There may even be times when abrupt and long-term changes take place. Examples include

groundwater flooding when groundwater tables may rise as much as 12 feet in one season leaving

formerly dry ground inundated for the foreseeable future, or streams drying up due to lack of recharge.

LAKES We believe that lakes will change because of climate change. Increased precipitation will increase

sediment and nutrient loads from runoff, particularly when the surrounding land use is agricultural,

developed, or undergoing development. When lakes become enriched with nutrients and sediments,

their trophic status is likely to change over time and water quality may decrease. Flooding may allow

waterbodies to become interconnected, spreading invasive species from one lake to another. Flooding

can also lead to shoreline erosion, increase in property damage and dam failures.

Changes in lake levels will be affected by increased precipitation and also by drought. Shallow lakes are

most affected by lowered water levels as are the littoral zones of deep lakes. Seepage lakes are the

most sensitive to changes in precipitation and groundwater elevations. In some cases, a lake’s

chemistry can completely shift based on changes in its water source from precipitation and overland

flow to groundwater dominated. These changes are difficult to predict because of the cyclic nature of

Figure 2. From 1950-2006, Wisconsin as a whole has become wetter, with an increase in annual precipitation of

3.1 inches. This observed increase in annual precipitation has primarily occurred in southern and western

Wisconsin, while northern Wisconsin has experienced some drying. The southern and western regions of the

state show increases in baseflow, corresponding to the areas with greatest precipitation increases. (Sources:

Kucharik, et al., 2010 and Greb, unpublished data; map prepared by Eric Erdmann, DNR, 2010)

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droughts. Further, the climate models are less clear about predicting future precipitation forecasts at

this time.

Increased temperatures will change the biological composition of a lake. Species native to warmer areas

may survive in a future warmer Wisconsin. Species composition may shift from a predominance of

green algae to blue-green algae. Coldwater fish species may shift north and be locally extirpated due to

warmer water.

With increased temperatures, moderately shallow lakes may no longer stratify but mix continually.

Internal phosphorus loading would then play a dominating force in a lake’s dynamics and affect its

trophic status. We may see the ice-free period last longer and some lakes may not freeze at all.

RIVERS AND STREAMS The state’s thousands of miles of rivers and streams will also be affected by a changing climate.

Historical records show increases in precipitation result in increases in river and stream baseflow and

that decreases in precipitation lead to decreases in baseflow. We anticipate that the predicted

increased precipitation will lead to increased baseflow. Increases in winter and spring precipitation will

likely cause large runoff events resulting in soil erosion, channel erosion, increases in sediment and

nutrient transport.

Changes in precipitation patterns will result in changes to the size and shape of stream channels.

Channel-forming flows will occur more frequently resulting in channel widening and down-cutting.

These changes will reduce aquatic habitat and contribute additional sediment to our stream systems.

As is true with lakes, we expect that increases in temperatures will change fish species composition in

our streams. Coolwater and coldwater fish species may no longer dominate some of Wisconsin’s

stream. Lower baseflow would also change trout habitat.

GROUNDWATER Climate change will affect groundwater resources across the state. However, given the diverse geologic

and hydrogeologic conditions present within the state, the nature of the change will be site-specific,

depending on soil and land cover characteristics, topography, depth to bedrock, depth to groundwater

and land use practices. Climate change will alter groundwater recharge. The most significant impacts

will be on shallow groundwater systems rather than deep groundwater systems that are more resilient

to change.

Changes in recharge can also cause dramatic changes in the dynamics of lake, stream and wetland

systems. Decreased recharge would result in reduced flow from springs, lower baseflow in streams, loss

of some wetlands, and lower lake levels. An increase in the frequency of intense storms could recharge

groundwater levels to the point of rising about the ground surface, causing groundwater flooding

(Figure 3).

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Figure 3. Flooding in 2008 near Spring Green was caused by groundwater rising over the land surface. (Photo by

Madeline Gotkowitz)

A rising water table will also decrease the distance between the land surface and groundwater, making

the groundwater more susceptible to contamination.

Increased temperatures in Wisconsin, resulting in a longer growing season, could also place a greater

demand on our groundwater resources to be used for irrigation.

WETLANDS Wetlands are also vulnerable to the climate change. Changes in water levels will affect the range, and

extent of wetlands in the state. This includes conversion of wetland type and declines in wetland

biodiversity due to the proliferation of invasive plants. Changes in wetland hydrology and plant

composition will, in turn, alter some wetlands’ ability to provide important functions such as flood

storage, water quality improvement, shoreland protection, and breeding and foraging habitat for fish

and wildlife.

ADAPTATION STRATEGIES Our working group used results from our meetings and workshops to prioritize what we feel are the

highest priorities of climate change impacts on our water resources and to propose adaptation

strategies. All of these physical, chemical and biological impacts are anticipated to affect food webs and

ultimately, the status of Wisconsin’s rich fisheries. In many cases, these impacts will call for policy

changes.

This list represents the first, consensus-based attempt to develop water resources responses to climate change in Wisconsin. The impacts, in italics, are followed by adaptation strategies.

viii

Increased flooding will have impacts on urban infrastructure and agricultural land, especially in low-lying areas and large watersheds

Identify, map, and prioritize Potentially Restorable Wetlands (PRWs) in floodplain areas

Restore prior-converted wetlands in upland areas to provide storage and filtration, and to mitigate storm flows and nutrient loading downstream

Develop both long-term and short term changes to community infrastructure

Increased frequency of harmful blue-green algal blooms due to nutrient rich runoff, lake

stratification, and changes in water levels

Increase monitoring of inland beaches and develop better prediction tools for blue-green algal toxins and associated water quality in order to improve predictive capacity

Develop statewide standards for blue-green algal toxins and take appropriate action to protect public health

Conflicting water use concerns based on increased demand for groundwater extraction due to

variable precipitation projections and warmer growing season temperatures

Encourage large water users to locate in areas with adequate and sustainable water sources including large rivers or the Great Lakes

Encourage rural and urban water conservation through incentives and regulation

Promote integrated water management by planning water use based on long term projections of supply and demand and tied to land use and economic growth forecasts

Changes in seepage lake levels due to variable precipitation, recharge, increased ET. There are

additional implications for water chemistry, habitat, and shorelines

Enhance and restore shoreline habitat (coarse wood, littoral and riparian vegetation, bio-engineered erosion control) to withstand variations in water levels.

In headwater areas or near watershed divides, enhance infiltration by reducing impervious surfaces in urban/riparian areas and changing land management practices.

Change planning and zoning for lakeshore development to account for changes in water levels.

Adjust and modify expectations and uses of lakes, especially seepage lakes; recognize that some lakes are not suited for all uses.

Increased sediment and nutrient loading to surface waters during earlier and more

intense spring runoff events

Resize manure storage facilities, wastewater facilities, stormwater drains, and infrastructure to accommodate increased storm flows to protect water quality

Reverse the loss of wetlands, restore prior-converted wetlands to provide storage and filtration by mitigating storm flows and nutrient loading

Protect recharge/infiltration areas and riparian buffers to reduce overland flow of polluted run-off

Incorporate water management strategies based on climate projections into farm-based nutrient management plans

Increased spread of aquatic invasive species due to changes in hydrology, water

temperatures, and warmer winter condition

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We did not develop adaptation strategies for this impact for this report. Since this is a first draft working document, we know that additional adaptation strategies will be developed, evaluated and refined over the coming years, including a strategy for aquatic invasive species.

FUTURE RECOMMENDATIONS This report serves as the first assessment of the impacts of climate change on our water resources. The

mission of the working group is broad and is expected to continually develop in the future. We

anticipate that future reports will help further refine identification of impacts of climate change on

water resources but also adaptation strategies.

The WRWG recommends that detailed hydrologic budgets and models will need to be developed at

appropriate local scales (watersheds, aquifers) in order to develop suitable adaptation and management

strategies. The complexity of the state’s surface and subsurface geology, soils, land use, and land cover

patterns necessitates the need for appropriate down-scaling.

REFERENCES Greb, S.R. (Unpublished data). Historic Trends in Flows of Wisconsin’s Rivers and Streams. Wisconsin

Department of Natural Resources.

Kucharik, C. J., Serbin, S. P., Vavrus, S., Hopkins, E. J., & Motew, M. M. (2010). Patterns of climate change

across Wisconsin from 1950 to 2006. Physical Geography, 31(1)

Magnuson, J. J., Krohelski, J. T., Kunkel, K. E., & Robertson, D. M. (2003). Wisconsin's water and climate:

Historical changes and possible futures. In C. Meine (Ed.), Wisconsin's Waters: A Confluence of

Perspectives (pp. 23-36). Madison, WI: Wisconsin Academy of Sciences, Arts, & Letters.

CHAPTER I. DESCRIPTION OF THE WATER RESOURCES

WORKING GROUP

The mission of the Water Resources Working Group (WRWG) is to assess and synthesize climate change

impacts related to Wisconsin’s water resources and assist the development of adaptation strategies for

dealing with those impacts. The working group’s focus is to understand the implications of a changing

climate for inland water levels and flows, including lakes, rivers, wetlands (including coastal wetlands),

stream baseflows, and groundwater. Future efforts by this group or others will include more

comprehensive ecological assessments based on these physical drivers.

WORKING GROUP CHARTER AND PARTICIPANTS Many WICCI working groups were initiated prior to the formation of the WRWG in July 2009 and

although many of them addressed water-related issues to some extent, the WICCI Science Council felt

that a Water Resources Working Group would provide a more integrated assessment of the effects of

climate change on the myriad water resources in our state including lakes, streams, rivers, groundwater

and wetlands. Further, the group was asked to assess the hydrologic processes such as rising and falling

water levels, river and stream baseflows, surface and groundwater interactions, evaporation-

transpiration and other hydrologic processes. Our conceptual diagram of WRWG approaches and

activities are presented in Figure 4.

The Water Resources Working Group (WRWG) currently includes 25 members representing the federal

government, state government, the UW System, the Great Lakes Indian Fish and Wildlife Commission

and the Wisconsin Wetlands Association. Members are professors, research scientists, policy makers,

and outreach specialists and are considered experts in the fields of aquatic biology, hydrology,

hydrogeology, limnology, engineering and wetland ecology in Wisconsin. The inside cover of the report

lists the members of the working group and their affiliations.

2

Figure 4. Flow diagram of the Water Resources Working Group activities and anticipated outcomes

Form Water Resources

Working Group of state’s water

professionals

Water Resources

Working Group reviews

climate predictions

Assess potential climate

change impacts on state’s

water resources

Refine predictions?

Other WICCI working

groups

WICCI climate

group

Water Resource’s

response

Fund

research

Support

research Develop adaptation

strategies

Work with management

agencies, communities

Implement water

resources adaptation plan

Improved resiliency of

Wisconsin’s water resources

for climate change

Refine?

Wisconsin Climate

Adaptation Report(s)

3

Once the WICCI Science Council approved the WRWG charter (Appendix A), the group set out on an

ambitious schedule toward its first milestone--a draft working group report for the state’s first adaptive

assessment report to be reviewed in Fall 2010. A final adaptation report for WICCI is due in February

2011. Milestones for the working group is summarized in Table 1.

Table 1. WICCI Water Resources Working Group Activities

While the report is a major milestone of the WRWG, we anticipate that the group’s activities will

continually evolve, with an anticipated outcome expected to be improved management of Wisconsin’s

water resources to improve resiliency in the face of a changing climate.

IDENTIFYING RESEARCH GAPS During our initial WRWG meetings, members presented research they and their institutions are

currently conducting on water resources of Wisconsin. Chapter 6, Information Gaps—Research,

Inventory and Monitoring Needs, discusses these research projects and the need for additional research

in more detail. The list of research projects helped the group frame activities, and it allowed us to

initially identify gaps for future research.

In the summer of 2009, the WRWG was asked to prioritize climate-related water resources priorities for

two upcoming calls for research in the University of Wisconsin System. They provided comments for the

UW System’s portion of the Wisconsin Groundwater Research and Monitoring Program’s (WGRMP) call

for proposals, a collaborative effort led by the state’s Groundwater Coordinating Council. Objectives for

applications for the UW System funds distributed through this solicitation are determined by the

Groundwater Research Advisory Council (GRAC).

Several of the identified research needs were forwarded to a multi-agency solicitation for grant

proposals (the Joint Solicitation). Two projects were approved for funded beginning in March 2010

Date Activity

May 5, 2009 Met with WICCI Science Council to discuss formation of Water Resources Working

Group (WG)

May - June 2009 Developed draft charter; recruited members for WRWG

July 2, 2009 Initial WRWG meeting: roundtable; revise charter

July 20, 2009 WICCI Science Council approves charter

August 27, 2009 WRWG Meeting: updates, prioritization of research topics for UW-WRI proposals

September 21, 2009 All-WICCI Workshop; WRWG breakout discusses adaptation report outline

Fall 2009 UW-WRI Joint Solicitation for research released; Deadline December 2, 2009

December 17, 2009 WRWG work session to discuss adaptive assessment; Brainstormed impacts.

January 26, 2010 WRWG work session to further prioritize impacts, discuss vulnerabilities

January 26, 2010 After discussion of peer reviews, UW-WRI Advisory Panel approves two climate-related

water resources projects (developed using WRWG priorities).

February 12, 2010 Wisconsin Wetland Association WRWG workshop

February 25, 2010 WRWG work session to prioritize possible vulnerabilities

March 5, 2010 Wisconsin AWRA WRWG workshop

October 2010 Target date for first draft of Water Resources Adaptive Assessment Report

4

through the U.S. Geological Survey 104B research program and are discussed more thoroughly in

Chapter 6.

PROCESS TO IDENTIFY CLIMATE CHANGE IMPACTS AND ADAPTATIONS In order to identify the potential effects of climate change on the state’s water resources and to develop

possible adaptation strategies, the WRWG was presented with the following question:

Based on the latest climate projections for Wisconsin, and your professional

experience in your field of expertise, what are the possible (or most likely)

impacts to water resources and/or hydrologic processes on the landscape that

would be important to communicate to the people of Wisconsin at this time?

Over the course of several meetings from July 2009 through February 2010, the group discussed these

questions for hydrologic processes, lakes, streams and rivers, groundwater, and wetlands. In addition,

we hosted workshops at two professional meetings and invited other water resource management

professionals and other stakeholders to address these questions. The groups were the Wisconsin

Wetlands Association meeting on February 12, 2010 in Eau Claire (Figure 5); and the Wisconsin Chapter

of the American Water Resources Association meeting on March 5 in Middleton.

Figure 5. Participants at the Wisconsin Wetlands Association meeting contribute their professional judgement

regarding possible climate change impacts on wetlands. (Photo: Kyle Maygera, Courtesy of Wisconsin Wetlands

Association)

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ONGOING ACTIVITIES AND FUTURE PLANS The WRWG has an ambitious plan for the coming years (Figure 4) and the first adaptation assessment

represents only one of many planned activities for the group. We plan to meet regularly -- at least four

times a year – to discuss ongoing research, promote research on priority issues, and discuss refinements

of climate and hydrologic modeling and projections. We expect to sponsor workshops and hold special

sessions at state and regional meetings to discuss our progress. We plan to interact with other WICCI

working groups and the outreach committee and regulatory agencies to continue to develop and

implement adaptation plans for protection of Wisconsin’s water resources.

CHAPTER II. WISCONSIN’S WATER RESOURCES

Wisconsin’s water resources are so ingrained in who we are that they help define our state’s borders:

Lake Superior to the north, Lake Michigan to the East, and the Mississippi River to the west. Our water

resources are vast (figure 1, page ii) and with new mapping technology and satellite imagery, the

Department of Natural Resources estimates that we have over 84,000 miles of streams, not the 57,000

miles as previously thought (DNR, 2008). We are now able to account for smaller streams and those that

flow only during wet seasons. There are more than 15,000 lakes, comprising 1.2 million acres of inland

waters. Wetlands cover 5.3 million acres of the state, and there is enough groundwater to cover the

entire state of Wisconsin to a depth of 100 feet.

The waters of our state are connected through the hydrologic cycle (Figure 6). As we discuss the

implications of climate change on our waters, we must recognize the significance of their connectivity.

Although much of this report is subdivided into separate resource types—lakes, rivers and streams,

Figure 6. Climate change may alter the way water moves through the water cycle.

8

groundwater and wetlands—the cycle cannot be separated. What happens in one part affects the rest.

As atmospheric water falls to the earth, water in wetlands, streams, and lakes flows to and from the

groundwater, recharging its reserves. Groundwater feeds into surface waters. Finally, water returns to

the atmosphere where it either evaporates or is transpired by plants (WASAL, 2003). All components of

the water cycle have impacts on people, plants and animals that use these resources.

Wisconsin has a tremendous variety of lakes, including the internationally significant Great Lakes. Lake

Superior is the largest freshwater lake in the world in terms of surface area, and one of the deepest at

1,332 feet. Lake Michigan is the sixth largest lake in the world and has a maximum depth of 925 feet.

Two-thirds of our state’s inland lakes are less than ten acres, while the largest is the 137,708-acre Lake

Winnebago.

Our lakes come in all shapes, sizes and depths. Some lakes have no inlets or outlets, some are

connected to groundwater and streams, and some are part of major flowage systems. Lakes have

variable trophic statuses, ranging from nutrient-rich eutrophic water bodies to nutrient-poor

oligotrophic systems. Land use has a tremendous influence on the quality of each lake, and those that

are surrounded by agricultural and urban land use are generally more enriched than those that are

located in forested watersheds.

Like the Great Lakes, the Mississippi River is significant nationally and internationally. Two-thirds of our

state drains to the Mississippi River while much of the remainder drains to Lake Michigan; a tiny fraction

drains to Lake Superior. The Wisconsin River and the Lower Fox River have contributed to the state’s

industrial and manufacturing success by providing storage reservoirs, hydroelectric dams and sites for

paper mills. In contrast, the state is also home to federally-protected wild and scenic rivers, 1,600 miles

of stream and river miles that are described as outstanding with extremely high quality water, and over

2,700 trout streams.

Like our lakes, streams and rivers display different characteristics. The differences are attributed to

physical differences such as the watershed size, topography, land cover and land use; source water (rain

or snow, groundwater or wetlands) and volume; stream gradient; stream geology; and stream channel

characteristics (WASAL, 2003).

It is hard to imagine how vast our state’s groundwater resources are because they are not visible to us.

But the 1.2 quadrillion gallons of water that lie beneath the surface in four different major aquifers play

an important role to our state’s natural and built environments. The majority of the state’s population

relies on groundwater for its drinking water, as do many other industries including agriculture. Less

than a third of the 32 inches of annual average rainfall recharges our aquifers each year (UW-Madison,

WRI, 2007). What precipitation doesn’t percolate into the ground is used by plants, evaporates, or

drains into our lakes, streams and rivers, reminding us again of the importance of the

interconnectedness between the different components of the hydrologic cycle.

Wisconsin has twelve different wetland types (Figure 7) ranging from forested to Great Lakes coastal

systems. The land area that comprises Wisconsin originally contained about 10 million acres of

9

wetlands, but only about half of that remain. The rest have been drained or filled. Five types of

forested wetlands encompass approximately 47 percent of all wetland acres in the state.

Wetlands are quite variable because of differences in soil type, water chemistry, the types of plant

materials they contain, and how wet they are. Wetlands serve an extremely important role in our

environment because of they are part of both land and water ecosystems. Wetlands can support a wide

variety of plants and animals, including vertebrates, invertebrates, plans and microbial life. Wetlands

can store water and act as filtration systems to downstream bodies of water, but they also can be places

of discharge.

Marsh Fen Sedge Meadow

Low Prairie Alder Thicket Open Bog

Ephemeral Pond Shrub Carr Coniferous Bog

Coniferous Swamp Floodplain Forest Lowland Hardwood Swamp

Figure 7. Wisconsin’s 12 wetlands types. All photos courtesy of the Wisconsin Wetlands Association

CHAPTER III. HISTORIC TRENDS IN WATER RESOURCES IN

WISCONSIN To better understand how projected climate change may affect the state’s water resources, and to place

future projections into the context of historical variability, it is important to understand trends of the

past. We used historic records for ice cover, lake levels, groundwater levels, and streamflow to answer

the following questions:

Is there evidence of climate change in the historical records for ice cover, lake levels, and streamflow?

Are recent climate trends found in temperature and precipitation (as presented by the Climate Working Group) reflected in the historical water records?

Are recent trends (over the past 25-50 years) consistent with the future projections being made with the General Circulation Models (GCMs)?

ICE COVER DATA Variability in lake ice cover is quite sensitive to changes in weather and climate (Magnuson, 2002) and

was considered one of the most sensitive responses of inland waters to climate warming by the

Intergovernmental Panel on Climate Change in their 2001 assessment (Gitay et al. 2001). Ice cover

records throughout the northern hemisphere were used to demonstrate long-term climate changes that

have occurred over the past 150 years (Magnuson et al., 2000; Robertson et al., 1992) and short-term

annual effects on weather associated with El Nino/Southern Oscillation Events (Robertson et al., 2002).

Decreases in the duration of ice cover in lakes throughout Wisconsin are the result of a combination of

later freeze dates, indicative of warmer fall air temperatures and earlier breakup dates, indicative of

warmer winter and spring air temperatures (Figure 8).

Detailed information on Shell Lake, Lake Mendota, and Geneva Lake are shown in Figure 9. The location

of each lake is shown in Figure 11 (Page 15). In these three lakes, the duration in ice cover in recent

years has decreased by about 10 to 40 days from that occurring near 1900. The largest changes have

been observed in Geneva Lake where for the first and second times on record the lake did not freeze in

two winters around 2000. However, the decrease in the duration of ice cover has not been linear and in

fact, there has been a slight increase in the number of days frozen duration in recent years. Note that

the most recent 10-year moving average values for all three lakes (horizontal blue lines in Figure 9), is

shorter than any other historical period including the warm period in the 1930s.

12

Figure 8. This illustration shows that over the past 150 years ice cover occurs later and breaks up earlier. The

circles indicate the location of the lakes and the colors key to the trends. (Adapted from Magnuson et al., 2003)

A detailed examination of the ice records for Lake Mendota show that the total duration of ice cover has

declined at a rate of 1.9 days per decade, or 19 days per century (Figure 10). The shortest period of ice

cover for the lake was 21 days in the winter of 2001-02. This is in contrast to an average period of ice

cover of about 100 days in the 154-year long record. The change in ice cover can also be seen in the

occurrence of extreme years. The winters with the 10 longest periods of ice cover (blue circles) all

occurred prior to 1900, while the winters with the 10 shortest periods of ice cover (red circles) mostly

occurred in recent years.

Short-term meteorological variability is also reflected in the ice cover of lakes. Unusually mild, late

winter air temperatures have been shown to occur in years of strong-to-moderate El Nino/Southern

Oscillation events and result in unusually early ice break up (Robertson et al., 2002). These effects are

superimposed on the long-term effects of changes in climate.

13

Figure 9. Annual ice duration for three lakes in Wisconsin. The 10-year moving average and most recent 10-year

moving average value are identified. See figure 6 for locations of the lakes. (Source: U.S. Geological Survey data)

14

Figure 10. Ice duration of Lake Mendota. The straight line indicates an overall decrease of 19 days per century in

ice cover during the 154-year period of record. The winters with the 10 longest periods of ice cover are identified

with blue circles and the 10 shortest periods of ice cover are identified with red circles. (Prepared by John J.

Magnuson, University of Wisconsin-Madison Center for Limnology.)

WATER LEVELS Water levels of lakes and shallow groundwater tables reflect the effects of hydrologic processes within a

given landscape. Changes in the water level of lakes and groundwater can be the result of either natural

climatic phenomena or other changes in their watersheds, such as changes in land use. Based on results

from general circulation models, many scientists believe that future climate change will cause changes in

the hydrologic budgets in specific geographic areas. These changes are expected to either cause higher

or lower lake and groundwater levels, or cause wider fluctuations in level than previously experienced

(Bates et al., 2008).

LAKE LEVELS Long-term records of water levels exist for only a few lakes in Wisconsin, three of which are shown in

Figure 12; their locations are on the map in Figure 11 (Page 15). These time series demonstrate both

long-term changes in water level over the past 40-70 years, and shorter-term cycles in water level of

about 10-15 years. These trends appear to vary throughout the state.

In the central part of the state, water levels have been variable and are currently low, but not as low as

in the 1930s and 1960s. In the southern part of the state, water levels appear to have increased since

the 1960s.

15

Figure 11. Location of data points for ice duration, lake levels and groundwater levels. (Map prepared by Dale

Robertson, U.S. Geological Survey, May 2010.)

16

In the southern part of the state, water levels in most seepage lakes have increased presumably due to

changes in the amount and timing of precipitation, and changes in land use in the watershed. (WICCI

Stormwater Working Group Report, 2010). The U.S. Geological Survey and Wisconsin DNR have now

begun a program to monitor water levels in a small number of lakes throughout Wisconsin.

In the northern part of the state, the water level of most lakes has declined in recent years. However,

long-term records show that the water level of Shell Lake in the northwest part of the state increased

until the early 2000s when precipitation decreased. Long-term records for this lake suggest that high

water levels around 2000 were the highest water levels since the late 1800s when water levels were

significantly higher than they are today. (Data observations before those in Figure 12 are anecdotal

information only.) It should be noted that the City of Shell Lake estimates indicate that about 3 billion

gallons of water (about 3 feet of stage) were diverted out of the lake from 2003 to 2005, which is a

substantial reason why the water level has declined since the peak in 2003.

In the north central part of the state, the recent low water levels is a continuation of a downward trend

that has resulted in water levels of many lakes currently being at the lowest levels in their measured

record. Water levels in most seepage lakes in north central and northeastern Wisconsin are at the

lowest level in the past 60 years.

Figure 12. Annual water levels for three lakes in Wisconsin. (Source: U.S. Geological Survey data)

17

Figure 13. The water levels of Anvil Lake are characterized by oscillations. The low levels reached between 2004

and 2010 are the lowest observed to date and are associated with the low precipitation in Northeastern Wisconsin

in recent years. (Source: U.S. Geological Survey data)

Anvil Lake (Vilas County), a northern Wisconsin seepage lake with a 74 year water level record,

demonstrates pronounced, recurring highs and lows (Figure 13). The record appears to indicate that

lake levels are getting progressively lower during each succeeding dry period and especially during the

present period for this lake in Northeastern Wisconsin. In the future, any water loss through

evapotranspiration associated with warmer temperatures would exacerbate any drought effect if

increases in evapotransporation exceed any increases in precipitation, as future climate scenarios

suggest. Other lakes and wetland systems that are high in the landscape where water levels are

dependent on local groundwater inputs and direct precipitation countered by evaporation are expected

to be subject to this same phenomenon.

18

During periods of low water level, Silver Lake is

oligotrophic with low phosphorus concentra-

tions and very good water clarity. During periods

of high water levels, however, the lake becomes

eutrophic with high phosphorus concentrations

and poor water clarity (Robertson et al., 2009a).

Silver Lake is located in part of Wisconsin (Figure

11) where phosphorus concentrations in surface-

water runoff are relatively low and where dilution

of the phosphorus loading would most likely

occur. Deep lakes in areas of greater

development may have higher phosphorus

concentrations in stormwater runoff. We can

expect that increases in precipitation from climate

change will result in degraded water quality.

Increases in precipitation and water level are

expected to increase the productivity of stratified

lakes. It should be noted, however, that the

response of shallow, more-frequently mixed lakes

may be quite different. The effects of changes in

water level in shallow lakes are now being

examined in a shallower system: Shell Lake in

Washburn County.

Dale Robertson, U.S. Geological Survey

It is difficult to predict changes in lake levels in

specific geographic areas using the results of large

global and regional circulation models because

the hydrological cycle involves many interrelated

components. These include climatic factors such

as precipitation patterns, water temperatures,

evaporation rates, groundwater inputs and

outputs, and runoff rates; and anthropogenic

factors such as changes in land use. Since changes

in the water level of lakes are driven by hydrologic

changes that my affect the nutrient loading to

lakes, it is thought that changes in water level may

affect the water quality, or productivity, of lakes.

The U.S. Geological Survey (2009a and 2009b)

analyzed how changes in the hydrology and water

level affect the productivity of deeper, stratified

lakes by examining Whitefish Lake in Barron

County and Silver Lake in Douglas County. The

two relatively pristine lakes have contrasting

drainage basin to lake area ratios which result in

differences in variability in their hydrological

processes and nutrient loading. Both studies

demonstrated that changes in hydrology that

result in increased water level and increased

nutrient loading also result in deeper stratified

lakes becoming more eutrophic.

Figure 14 (next page) demonstrates the changes in

Silver Lake which has a larger drainage area and

more relative loading. Its response to changes in

hydrology and water level was much more

extreme than Whitefish Lake.

Case Study—Silver Lake, Barron County

Effects of Water Level Change on Productivity of Deep Lakes

19

Figure 14. Trophic state index (TSI) values based on surface concentrations of total phosphorus and chlorophyll a,

plus Secchi depths, in Silver Lake, Barron County, Wis., 1986 to 2008 (Robertson et. al, 2009a).

20

1930 1940 1950 1960 1970 1980 1990 2000 2010

88

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ft)

1930 1940 1950 1960 1970 1980 1990 2000 20101930 1940 1950 1960 1970 1980 1990 2000 201088

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La

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core of Berry Lake, representing about 200 years of its

history. The core was analyzed for geochemical parameters

such as phosphorus, nitrogen, and titanium which is a

surrogate for soil erosion.

The diatom community in the core was also analyzed.

Diatoms are an alga that have shells made of silica allowing

them to be deposited and fossilized in lake sediments. These

algae have unique nutrient and habitat requirements that

can be used to estimate past phosphorus concentrations.

Cluster analysis indicates that the diatom community can be

divided into three time periods: no shoreline development,

early development, and late development with the highest

housing density. The analysis shows that there is no

relationship between nutrient concentrations and water

levels. Even when water levels were their highest in the 65

year record (1985), no detectable increases in phosphorus

were seen.

This study indicates that the changes in nutrient loading

associated with land use changes may be much larger than

the changes in loading resulting from large fluctuations in

hydrology and water level that would come from climate

change. In deeper, larger lakes, the importance of changes in

nutrient loading from land use and climate change may be

less important than in shallow lakes because their larger

volumes that can dilute the changes in nutrient loading.

Paul Garrison, Wisconsin Department of Natural Resources, Unpublished data

Studies have shown that flooding terrestrial landscapes,

such as reservoir creation, results in episodic inputs of

nutrients. It has been hypothesized that the flooding of an

exposed shoreline following low water levels may introduce

significant amounts of nutrients to the lake. Conversely,

during very high water levels, bank erosion also may supply

nutrients to the lake.

Berry Lake, Shawano County, is a shallow, seepage lake that

is located high in the ground watershed resulting in large

fluctuations in the lake’s water level. There are almost 70

years of continuously recorded lake levels, beginning in

1942 (Figure 15). A reliable lake level record is also

available from 1934 which is significant because that was

during the extended drought of the 1930s. This lake

represents a good opportunity to estimate which is more

important: fluctuating lake levels or changes in land use in

the watershed.

Berry Lake also has a high degree of shoreline development.

At present, the housing density is 13.6 homes per mile

which is similar to the density of homes around many lakes

in southeastern Wisconsin. This lake represents a good

opportunity to estimate whether fluctuating lake levels

cause larger changes in the amount of nutrient reaching the

lake than changes in land use.

Analyzing a sediment core of a lake is one method of

evaluating its history, including fluctuating lake levels

through flooding and drought and estimating historical

nutrient levels. DNR’s Bureau of Science Services took a

Case Study – Berry Lake, Shawano County

Short Term Water Level Changes

Figure 15. Lake level

recorded at the Notbohm

family cottage on Berry

Lake. Lake resident James

Chadek recorded the

1934 level. During this 75

year record, the lake level

has fluctuated a

maximum of 8 feet. (Note

all water levels were

estimated from

measurements from a

defined location to the

edge of the lake.)

21

lakes may become seepage lakes resulting in changes

in their geochemistry and a shift in their biological

communities.

Paul Garrison, Wisconsin Department of Natural Resources, Bureau of Science Services, Unpublished Data

Terrestrial pollen studies indicate that the climate

4,000-6,000 years ago in the Upper Midwest was drier

and apparently warmer than at the present time. This

historical climate may be similar to the future climate

predicted by many general circulation models.

Although these models predict more precipitation in

some areas, warmer air temperatures causing higher

evapotranspiration rates may result in more drought-

like conditions than experienced today.

Max Lake, is a seepage lake located at relatively high

elevation in the landscape (Figure 16) in Vilas County.

It has very soft water and a pH of 5.0-5.5. A sediment

core taken from the lake spanning 13,000 years allows

us to explore how a warmer and apparently drier

climate may affect lakes.

The diatom community in the core suggests that for

the first 6,000 years after its formation, Max Lake was

a drainage lake with a pH level of 6.5-7.0 and

experienced periodic flooding events. The sediment

stratigraphy and diatom community suggest that

during the drier and warmer period 4,000-6,000 years

ago, the lake became a seepage lake. As a result, most

of the hydrologic input to the lake switched from

surface- and groundwater-fed to nearly all

precipitation-fed, much like the left-most lake in Figure

17 (next page).

Following the return to a cooler, wetter climate, the

lake did not switch back to a drainage lake but

remained the soft water seepage lake we see today

with low pH levels and minimal groundwater input.

Examining the long-term core from Max Lake may

allow us to understand how climate change may affect

drainage lakes that are at higher elevation in the

landscape today. As the climate becomes warmer and

evapotranspiration increases, some of these drainage

Case Study Max Lake, Vilas County

Long Term Water Level Change

Figure 16. From high to low in the landscape,

hydrologic connectedness ranges from isolate seepage

lakes (top of diagram) to lakes connected by streams

(middle of diagram) to large river systems (bottom

diagram). (Source: Magnuson et al., 2006)

22

Figure 17. Lake hydrology, combined with a lake's position in the landscape, are important for understanding how

lakes will respond to changes in precipitation and increased evapotranspiration. (Adapted from Webster et al.,

1996)

GROUNDWATER LEVELS Similar to lake water levels, fluctuations in shallow groundwater levels occur as a result of changes in the

hydrology of an area. Only a few long-term groundwater-level records exist in Wisconsin. Of those, a

few of the longest records are shown in Figure 18. While the water levels in these wells have not been

rigorously analyzed for trends, they appear to show relatively large water level fluctuations on the order

from annual- to multi-decadal oscillations. Interestingly, these three example wells from northern and

southern Wisconsin appear to follow similar patterns over some eras (1965 - 1990), but follow different

patterns at other times (1950 - 1965 and after 1990).

Figure 18. Groundwater levels for

three wells in Wisconsin show that

oscillations in water level can range

in length from annual to multi-

decadal. (Source: U.S. Geological

Survey data)

23

Similar to lake levels during the past few years, water levels in the south have increased due to several

years with high precipitation. Water levels in the north, especially north central areas, have decreased

during years with low precipitation. While local and site-specific conditions control water level response

to hydrologic drivers, groundwater and lake levels often show similar patterns and are useful for

evaluating regional patterns and long-term change.

HISTORIC TRENDS IN FLOWS OF WISCONSIN RIVERS AND STREAMS To understand how projected climate change may affect river flows in streams, Wisconsin DNR’s Bureau

of Science Services analyzed 57 years of flow data collected by the U.S. Geological Survey from 48

stations (Greb, unpublished data). This analysis allows us to put anticipated changes in hydrologic flows

in the context of historic changes.

Appendix 3 provides the methodology and detailed results of these analyses.

During the 57-year study period, statewide precipitation increased approximately 10-15 percent.

Interestingly, the average statewide (based on the 48 stations) percent change in annual flows observed

over this same 57-year period also increased by about 14 percent, suggesting a strong coupling between

basin precipitation and river flow (Figure 19).

Figure 19. From 1950 to 2006, Wisconsin as a whole became wetter, with an increase in annual precipitation of

3.1 inches. This observed increase in annual precipitation was primarily in southern and western Wisconsin, while

northern Wisconsin was drier (Center for Climatic Research & Center for Sustainability and the Global

Environment, Nelson Institute, University of Wisconsin-Madison). The southern and western regions of the state

had increases in baseflow (left) and annual flow (right) between 1950 and 2006, corresponding to the areas with

greatest increases in precipitation (Greb, unpublished data; maps prepared by Eric Erdmann, 2010).

24

For the next half century, precipitation projections among the different climate models increase on

average 2 to 7 percent which is less than the increases in precipitation we have seen over the past half

century. Figure 12 in the WICCI Climate Change Working Group report has maps that show these

projections.

Will this translate into a corresponding change (2 to 7 percent) in annual flow for the state? Possibly,

provided other conditions remain constant, but seasonal precipitation patterns and extreme events are

also expected to change, which could impact runoff amounts and consequent flows. In addition,

temperatures are projected to increase, which will increase potential evaporation and decrease water

yield to the receiving waters. Finally, land use changes, both rural and urban, will influence water cycle

components (i.e. groundwater, infiltration) and resultant river flows.

Given that annual flow characteristics are a product of multiple factors, it is difficult to predict changes

in future flows. Hydrologic modeling on a basin scale, which simulate these dynamic hydrologic

processes and account for changing land use conditions, temperature regimes, precipitation timing and

characteristics, are needed to fully understand the impact of future climatic conditions on Wisconsin’s

river and stream flow regimes.

COMPARING THE PAST WITH THE PROJECTED FUTURE We evaluated historical precipitation intensity data from several Midwestern states including Wisconsin

using the Rainfall Frequency Atlas for the Midwest (Huff and Angel, 1992). We used records from 409

stations with at least 44 years of data. The purpose of this analysis was to provide a comparison of

historical return period records to the WICCI projections for the future. Return period, or recurrence

interval, is the average interval of time within which the given event will be equaled or exceeded at least

one time.

The WICCI projections using the A1B scenario indicate that the 2-inch precipitation events will increase

from 2 - 3.5 days per decade, depending on the location in the state (Center for Climatic Research &

Center for Sustainability and the Global Environment, Nelson Institute, University of Wisconsin-

Madison).

Climatic sections 3 & 6 (Figure 20), which cover the northeast and east-central portions of the state, were combined because they had a longer return period than the remainder of the state. The return period for Sections 3 & 6 was about 400 days, 13.2 months or 1.1 years which is equivalent to 9.1 days/decade. The WICCI models project that 2-inch precipitation events will increase 2.5-3.5 days per decade which would be an increase of 27-39 percent.

Figure 20. Climatic sections for Wisconsin (Huff and Angel,1992). Green

and light green colors indicate sections with similar return periods for the

24-hour, 2-inch precipitation event.

25

The return period for all other climatic sections in Wisconsin was about 250 days, 8.2 months or 0.68

years (Figure 21) which is equivalent to 14.6 days/decade. The WICCI models project that 2-inch

precipitation events will increase 2-3 days/decade, representing an increase of 14-21 percent when

compared to the historic record.

Figure 21. Historical data showing the 24-hour precipitation amount vs. average return period for two groups of

climatic sections in Wisconsin. Triangles depict the return period for a 2-inch precipitation. (Graph prepared by

Dale Higgins, U.S. Forest Service.)

TRENDS IN WETLANDS – LOSS OF WETLANDS OVER TIME Little or no data are available regarding trends in the hydrologic conditions of wetlands, especially in

relation to historic precipitation and temperature. However, wetlands have historically been under

stress from a variety of activities. According to the Department of Natural Resources, Wisconsin has lost

about 4.7 million of the 10 million acres of wetlands that were present in 1848 due to farm drainage and

filling for development and roads.

The DNR prepares an annual report that compiles information from databases that track regulatory

permits, compensatory mitigation projects, Department of Transportation mitigation projects and

restoration activities carried out by a partnership of federal and state agencies and conservation

organizations. Positive gains and losses to the state’s wetlands are tracked. For example, in 2007, about

3,615 acres were either restored or enhanced while 537 acres were either filled or disturbed.

Transportation projects and or utility line work account for the majority of these filled or disturbed

wetlands (DNR, 208).

While the conversion of wetlands to other uses has slowed, they continue to be destroyed and degraded

due to invasive plants, overuse of groundwater, increased stormwater from development and other

26

changes in land use. The DNR used Landsat imagery to map wetlands dominated by invasive reed canary

grass (Phalaris arundinacea) across the entire state at a minimum map unit of 0.5 acre. They found

498,250 acres of wetland are dominated by reed canary grass.

WATER RESOURCES TRENDS ANALYSIS The analysis of historical data shows that Wisconsin’s water resources are intimately linked to local and

regional climate conditions. Long-term records of lake water levels, lake ice duration, groundwater

levels and stream flow are correlated with long-term trends in atmospheric temperature and

precipitation.

Analysis of 60 years of Wisconsin’s climate data (Kucharik et al., 2010) further suggest that future

climate projections will affect our state’s water resources in both quantity and quality. However, there

may be different hydrologic responses to climate change in different geographic regions of the state. This

is clearly evident in analysis of past trends in Wisconsin.

27

CHAPTER IV. CLIMATE ASSUMPTIONS, DRIVERS AND

UNCERTAINTIES

In preparing this report, the Water Resources Working Group used the climate change projections,

probabilities and modeling results generated by the Climate Working Group to better predict what

changes we might expect to the state’s myriad water resources. Table 2 is a summary of the predictions

that were used to help us make our predictions.

Table 2. Predictions in temperature and precipitation that will affect Wisconsin’s water resources.

Temperature

The temperature will increase in all four seasons.

The greatest increase in temperature will be in winter and the least temperature increase will be in the fall.

The greatest temperature increase will be in northern Wisconsin

Temperatures will become more homogeneous statewide, with little difference between north and south.

The number of extremely cold days will decrease, particularly in northern Wisconsin.

The number of extremely warm days will increase, particularly in southern Wisconsin.

Lake Michigan and Lake Superior will moderate increased warming trends in near shore areas.

Precipitation

Precipitation will increase in fall (November), winter (December, January, and February) and spring (March, April, and May).

Precipitation is not expected to increase in summer.

Precipitation will increase by 10-20 percent in winter.

Precipitation will increase slightly more in northern Wisconsin in winter and spring, but not in summer and fall.

Large precipitation events (greater than 2” of rain in a 24-hour period) will increase statewide.

Large precipitation events will increase the most in northern and eastern Wisconsin.

Large events may increase by 15 to 35 percent or 2-3 times per decade.

The probability that precipitation will fall in a frozen form will decrease statewide.

Increased temperatures may have an enormous effect on lakes, streams and wetlands. Some of the

effects include:

Average surface water and shallow (under 100 feet) groundwater temperatures may increase.

There may be a longer ice-free period.

Ice thickness may decrease.

Potential evapotranspiration rates may increase.

Freeze-thaw events may increase.

28

Changes in precipitation, either by way of flood or drought, will also impact our water resources. Some

of the effects include:

A longer recharge season due to increase in precipitation in winter and spring.

Changes in recharge and discharge based on precipitation falling in the form of rain versus snow.

CLIMATE DRIVERS Climate drivers are those things that may cause changes to the resource. The main drivers

we identified are large rainfall events, water availability, and warming temperatures.

Large rainfall events are thought of as rainstorms that are high in intensity and rain that falls at times of the year when resources are most vulnerable to change.

Water availability could be either positive, such as flooding, or negative, such as a drought. Too much or too little precipitation can affect water resources. Water availability varies across the state, as indicated by the WICCI climate change maps. The seasonal variation in temperature will also affect the form of precipitation, particularly through less snow.

Warming temperatures for both air and water are expected throughout Wisconsin, and should produce longer ice-free periods in the winter, and an increase in potential evapotranspiration (ET).

UNCERTAINTIES Some of the model projections express uncertainty in terms of impacts on water resources.

Uncertainties include the role of potential evapotranspiration (ET), frozen ground in winter, uneven

precipitation throughout the state, the inability to predict convection storms in the summer, the role of

land use in precipitation events, and the inability to predict the frequency of storm intensity.

Potential evapotranspiration represents the amount of water that could be evaporated from land,

water, and plant surfaces when there is adequate water for plant growth in the soil. It is largely driven

by temperature and solar radiation. The WICCI Climate Change Working Group projects that ET will

increase in most locations in the state because of the warmer conditions, most notably in spring and

then in autumn (Figure 19 in their report). Winter and summer will see smaller changes in potential

evapotranspiration because rising temperature will be offset by a moister atmosphere. So, while

summer precipitation may increase, potential ET may have a stronger influence resulting in decreasing

lake levels.

The role of potential evapotranspiration and its effect on the water budget has been identified as one of

our group’s key research needs in climate projections. As a result of a request for proposals, a Wisconsin

research project was funded beginning in March 2010 to help answer some of these questions (Chapter

6). The project will examine how the second largest component of the water budget, ET, will be

29

affected by climate change effects such as increasing temperature, lengthening of the growing season,

increased atmospheric carbon dioxide concentrations enhancing water use efficiency, changes in

relative humidity, and changes in soil water availability.

The climate change models project that snow will melt earlier and that the ground will thaw earlier

(Figures 14-18 of the WICCI Climate Change Working Group Report) affecting the state’s water

resources. If the ground is frozen, precipitation will runoff into surface water when it melts or if it falls

as rain. On the other hand, if the ground is not frozen when precipitation falls, it will infiltrate into the

ground and recharge groundwater. In some situations, this may result in groundwater flooding.

Precipitation is expected to increase across the street over the next 50 years. However, since

precipitation does not fall uniformly throughout the state, there is uncertainty about how it will affect

water resources on a local scale. To make better predictions, we need to have more fine-scaled maps,

ideally on a watershed scale. Additionally, we need watershed scale modeling of stream flow.

The existing models do predict the larger-scale convective conditions that are well-correlated with

summer convective rainfall. However, they have relatively greater difficulty in predicting convective

storms—storms where tornadoes, hail and flash-flooding may occur—at a small spatial scale than

general large cyclonic storm rainfall at the larger spatial scale.

Localized storm events highlight the significance of land use and how different heavy localized events

can impact an area (Figure 22). In urbanized areas, short-term but intense rainfall may lead to flash

flooding. Where land is not developed, this same type of storm would be infiltrated into the ground.

Wetlands have the capability to act as flood storage areas, so where wetland acreage exists, flooding

will have less of a negative impact. Convection storms will have a much more significant impact where

land is moderately to highly developed.

Figure 22. About 4 inches of rain

fell in Madison on July 27, 2006,

resulting in major, but localized,

flooding on the UW-Madison

Campus. Photo: Gordy

Stephenson

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U.S. Geological Survey: Studies of Climate Change on a Watershed Scale

The U.S. Geological Survey has conducted studies to determine the sensitivity and potential impacts of long-term

climate change on freshwater resources in the United States on a watershed scale, beginning in 2008. The

modeling exercise used modified precipitation and temperature inputs with the mean monthly climate change

fields derived from the General Circulation Model simulations (IPCC, 2007). The long-term goal of the national

study is to provide the foundation for hydrologically-based climate change studies across the nation.

Black Earth Creek Basin

One of the basins for which the nation-wide modeling was calibrated is the Black Earth Creek Basin. Black Earth

Creek is a cold-water trout tributary to the Wisconsin River. Results show an increase in actual water lost from the

basin due to evapotranspiration (Figure 23 (a)). This loss is partially offset by projected future increases in

precipitation over the basin such that the downward trend in the annual streamflow is less apparant than might be

expected given the increase in ET.

Results further indicate that a decrease in snowpack and snow cover during the winter and early spring diminish

the importance of spring snowmelt to the stream (Figure 23 (b)). The characterization of upper Midwestern

streams as being spring snowmelt dominated may not hold if these scenarios of climate change represent future

conditions. Rather, the hydrology would resemble more southerly United States streams.

Soil moisture in the watershed is also expected to decrease, causing drier conditions during the growing season.

This may place more demand on groundwater resources to irrigate crops.

Figure23(a). Basin mean values of actual evapotranspiration. The horizontal black line represents 1988-2000 conditions; the

three solid colored lines indicate the 11-year moving mean values for the three future GCM scenarios (central tendency of the

five GCMs for each scenario). Evapotranspiration will increase to the point of water loss from the basin over time. (b)

Modeling results showing monthly changes in basin soil water due to changes in climate. The simulated amount of water

entering the soil is reduced, especially during the growing season.

(Source: Randall J. Hunt, John F. Walker, Steven M. Westenbroek and Steven L. Markstrom, USGS, unpublished data)

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Trout Lake Basin

A second basin being used for model calibration is

the Trout Lake Basin in northern Wisconsin which

includes the Trout River, the outlet from Trout

Lake. In this area, stream flow is dominated by

groundwater contributions, but surface water

runoff can occur during intense rainfall periods

and spring snowmelt.

Project results suggest smaller snowpack volumes,

a tendency for mid-winter melts, and a shorter

snow-covered season, beginning later and ending

earlier. This has implications for winter

recreation, and could potentially affect

phenological responses, with corresponding

changes in the ecosystem. Examples include

changes in migratory patterns of birds or spring

flowers blooming earlier than in the past (Bradley

et al., 1999).

The recharge results suggest a shift in the timing

of the recharge, reducing the importance of spring

snowmelt and increasing the occurrence of

smaller recharge events throughout the year. The

flattening of the recharge dynamic of this

northern temperate hydrologic system could

result in conditions more typical of a more

southern lake-stream watershed. This change

could also potentially affect the seasonal nature of

water budgets to lakes and the seasonal

distribution of streamflow, which both depend on

groundwater levels. As with the snow-covered

response, a shift in the timing of recharge could

alter phenological responses with associated

ecosystem changes.

The modeling results indicate a reduction of soil

moisture, which could potentially change the

overall vegetation in the system. This has obvious

ecosystem implications, and could potentially

result in a changed and less diverse plant

assemblage. Further, the system would likely be

more prone to fires, which could dramatically alter

the hydrologic response after a fire event.

One of the principle concerns in the Trout Lake

area is the fate of hydrologic budgets of area lakes

and resulting lake levels. This has wide ranging

implications for property values, recreational use

of the lakes, the hard-water/soft-water status and

trophic state of the lakes, and the biotic response

within the lakes. Because of the flat terrain,

coarse aquifer sediments, and precipitation rates

that are relatively higher than basinwide

evapotranspiration rates, groundwater has a very

strong influence on the hydrologic system in the

watershed (Figure 17 on Page 22). Therefore, a

more sophisticated representation of the

groundwater system would likely provide a more

representative view of the response of the basin

hydrology to change. A coupled groundwater-

surface water model (GSFLOW; Markstrom and

others, 2008) is being calibrated which will predict

the response of the full hydrologic system,

including groundwater and lake levels. This model

will allow a more complete assessment of the

response of the system to climate and land use

change.

(Source: Hunt, R.J., Walker, J.F., and Doherty, J., In Press)

U.S.G.S.: Studies of Climate Change on a Watershed Scale, (con’t.)

32

CHAPTER V. PROJECTED IMPACTS OF CLIMATE CHANGE

PROJECTED IMPACTS The working group and workshops at the WWA and AWRA meetings were able to identify multiple

impacts of climate change on our state’s lakes, rivers, streams and wetlands, as well as identify how the

hydrologic processes that govern these water resources may change in the future. The following is a

discussion of some of the resource impacts that were identified, and the drivers derived from the

climate models that may cause the impacts.

HYDROLOGIC PROCESSES Hydrologic processes are the ways water moves through the water cycle. The water cycle can be

simplified (Figure 6, Page7), but it is representative of how all water is interconnected. When one part

of the system is affected by the driving forces of a changing climate, all other parts are affected.

Spatially, the state’s hydrologic processes will not be affected uniformly. The differences reflect

variations in land use, soil type and surface deposits, groundwater characteristics, and runoff and

seepage responses to precipitation.

Regional differences in soil type and land cover will affect how climatic changes translate into hydrologic

changes. Sandy soils drain more rapidly than clay soils, and areas that are developed will see more

runoff than areas that are forested. These variations reinforce the statement that not all portions of the

state are expected to respond in a similar manner in hydrologic responses to climate change.

We expect that there will be system-wide changes in hydrologic processes but these may not be

completely predictable. There may even be times when abrupt and long-term changes take place.

Examples include:

Groundwater flooding, when groundwater tables may rise as much as 12 feet in one season leaving formerly dry ground inundated for the foreseeable future

Streams drying up due to lack of recharge

Change in species composition, such as a shift from green to blue-green algae in a lake

Most of the state is predicted to see more frequent precipitation events, including one-inch, two-inch,

and three-inch rainstorms (Figure 12 of the WICCI Climate Working Group Report). The next assessment

report may verify some of our predictions:

Where heavy rainfall becomes more intense, the hydrologic cycle may become more dynamic, with increased flushing of lakes and a decreased mean residence time.

Increased infiltration may lead to increased groundwater recharge to the point of groundwater flooding.

Increased spring precipitation will increase spring runoff. With increased winter temperatures it is not likely that snowfall will increase in the winter, but precipitation will fall instead as rain or freezing rain.

33

Increased intensity and increased magnitude of precipitation will affect the depth of plant propagation, water availability in the root zone and deep drainage systems. The duration between rain events will strongly effect the interception of water. When intercepted water is returned to the atmosphere, it does not lead to vegetation productivity.

There are also thermal impacts to water resources if atmospheric and water temperatures rise. Aquatic

systems can suffer if streams or other resources are taxed with a heavy influx of warm water, either

from overland flow, such as water picking up heat along a parking lot, or stormwater discharged from a

stormwater management facility.

Again, the length of time that the ground is frozen is an important variable in alteration of the

hydrologic cycle. Groundwater recharge depends on the timing of precipitation and warming

temperatures.

IMPACTS ON THE BUILT ENVIRONMENT There will also be general impacts on our built world and on human health. With increased heavy

rainfall events, current man-made controls would be overwhelmed, such as under-designed stormwater

detention basins. Other existing infrastructure may also be taxed, such as combined stormwater

overflow systems that will not be able to keep pace with increased volumes of stormwater.

The WICCI Stormwater Working Group Report (2010) analyzes the effects of a changing climate on

Wisconsin's precipitation patterns (rainfall and snowfall), and the resulting impacts upon high stream

flows and surface flooding, high water levels in lakes and impoundments, and high groundwater levels

and soil saturation. Their report discusses impacts on the infrastructure in detail.

LAKES Some of the most significant impacts on lakes from climate change will be from increased sediment and

nutrient loads due to increased precipitation, problems from aquatic invasive species, changes in species

composition, decreases in ice cover throughout the state, physical impacts on lakes, and changes in lake

levels.

INCREASED SEDIMENT AND NUTRIENT LOADS An increase in large intensity rainfall events will result in increased sediment and nutrient loads to lakes

from increased runoff from surrounding land and/or streams. Regional differences across the state will

depend on land use, soils and geology. Drainage lakes and impoundments will experience more impacts

than seepage lakes which are governed by groundwater.

The timing of increased precipitation is critical to the potential impacts on lakes. If the ground is frozen

but precipitation is in the form of rain, it will run off into surface waters carrying contaminants with it,

particularly the nutrients associated with soil and manure runoff. In contrast, when the ground is not

frozen, precipitation is more likely to infiltrate into the ground and recharge groundwater. However, as

rainfall intensity increases, more of the precipitation will run off as the ground becomes saturated.

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An increase in nutrient and sediment load to a lake will

likely increase its trophic status and over time, may reduce

its water quality. Variables like decreased water clarity can

have effects on many species such as loons and walleyes

that rely on sight to feed. Turbid, shallow lakes are often

dominated by fish that are not sight feeders such as carp

and bullheads. These fish will further stir up the bottom

sediments leading to even greater turbidity.

AQUATIC INVASIVE SPECIES Climate change may also increase the spread of aquatic

invasive species within and among lakes. During flooding

events, waterbodies may become interconnected, allowing

invasive species to spread from one lake to another. In

contrast, drought may bring about a new habitat that may

be well suited for an invasive species that may be

introduced.

Increased temperatures may also lead to new introductions

and survival of aquatic invasive species not previously

recorded in Wisconsin. Species native to warmer areas may

be more likely to survive when temperatures rise because

many species will be able to over-winter, such as Hydrilla,

water hyacinth, or the red swamp crayfish. These species

are native or well-established in the southern U.S., but are

thought to be limited by cold temperatures and ice cover.

However, two recent findings of Hydrilla and the red swamp

crayfish in small, constructed ponds have shown that

overwintering is possible, and will become even more likely

with shorter or lack of ice cover.

SPECIES AND HABITAT SHIFTS When temperatures in lake water rise, there is a greater

likelihood that species composition will shift. Increased

water temperatures may lead to an increased blue-green

algae growth which may impair a water body for

recreational and aesthetic purposes. An increase in

nuisance levels of blue-green algae growth is more likely to

occur in eutrophic or nutrient-rich lakes.

Increased temperatures may change the algal composition

of the lake entirely. Coolwater zooplankton with a higher

Case Study – Lake Mendota

Nutrient Loading

Water quality data from Lake Mendota,

Dane County, show that since 1980, the

lowest concentration of total

phosphorus (P) in the lake was in 1988

as a result of a two-year drought, with

reduced P loadings. Water clarity was at

its highest level during this time. In

contrast, in 1993, total phosphorus

concentrations were highest following

very high spring and summer runoff

events. These data point to the

importance of precipitation, runoff, and

its contribution to nutrient loadings in

the lake’s nutrient concentrations

The timing of precipitation events is

critical to nutrient loading to the lake.

Data analysis from 1990-2006 show that

48 percent of the total phosphorus

loading to the lake occurred between

January and March, with much of the P

in dissolved form. At other times of the

year, the load is bound with sediments

and capable of being deposited in lower

stream reaches before entering the

lake. The winter load is derived from

manure in the watershed.

Increased winter precipitation in the

form of rain falling on frozen ground, as

predicted by climate change models,

may increase the P load to the lake.

More intensive use of best management

practices in the watershed is essential to

reducing nutrient loading to the lake.

Source: Lathrop, 2007

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filtration capacity may be overtaken by warm water species and result in decreased water clarity and

dramatic changes in overall zooplankton and phytoplankton populations.

Fisheries and plant species are likely to transition to those that are more highly adapted to warmer

water temperatures. For example, coldwater species such as lake trout may shift further north and be

locally extirpated due to warmer water temperatures. The WICCI Coldwater Fish and Fisheries Working

Group discusses these projected changes more fully in their report (2010). Warm-water species such as

small-mouth bass and blue gills may expand to new habitats, changing existing food webs.

With increased temperatures, moderately shallow lakes may shift from mixing twice a year (dimictic) in

the spring and fall, to mixing continually (polymictic) during the ice free period. This continual mixing

may make internal phosphorus loading a dominant force in a lake’s dynamics and affect its trophic

status. Internal mixing might also take place earlier and then stimulate noxious plant or algae growth.

In a small number of incidences, increased algal growth may require more extensive treatment of

drinking water supplies placing additional costs on local communities.

CHANGES IN ICE COVER Climate models predict that ice cover will decrease throughout the state and there may even come to a

time when Wisconsin’s lakes are ice-free all winter. The environmental consequences of this are great.

Decreased ice cover may lead to an extended growing season in lakes, not just for aquatic plants, but for

green and blue-green algae. If there is more plant biomass, there may also be an increase in aerobic

decomposition in the summer, a shorter period of stratification and an overall increase in water

temperatures. In shallow and eutrophic lakes, a longer ice-free period may result in more frequent

winter fish kills.

Aquatic plant growth is likely to accelerate with increased temperatures. Less snow and ice cover will

allow plants to get a head start in the spring and become a nuisance during the summer.

PHYSICAL IMPACTS Drainage lakes and impoundments are more likely to suffer from physical impacts of increased

precipitation events. Flooding may lead to shoreline erosion, increase in property damage, and dam

failures. An example is the 14 inches of rain that fell in southern Wisconsin in June 2008. During this

intense rainfall event, the water in Lake Delton eroded through Highway A which served as an earthen

dam, washing out the road and houses. The lake essentially washed away into the Wisconsin River,

resulting in millions of dollars in damage.

CHANGING LAKE LEVELS Lake water level fluctuations are important to lake and water managers, lakeshore property owners,

developers, and lake users. Lake levels change from year to year, and extreme high or low levels can

present problems by restricting access to water and hampering navigation, flooding lakeshore property,

damaging shorelines and structures, and changing near-shore vegetation.

36

Figure 24. High water levels in southern

Wisconsin contrast with low water levels in

northern Wisconsin in 2008.

Photos by Tim Asplund

Climate forecasts show that precipitation changes in the state will not be uniform (Figure 24), and

changes in lake levels are difficult to predict because of the balance between evaporation versus

increased precipitation. If evapotranspiration is greater than precipitation and/or recharge, lake levels

will drop. If precipitation and recharge are greater, lake levels will rise. Or, they may balance each other

out. Seasonal variation in the prediction of precipitation and decade-scale variation also affect lake

levels, as was described in the historical case studies in Chapter 3.

Changes in lake levels, either up or down, will have impacts on aquatic habitats, including plants,

substrate and coarse woody vegetation. Shallow lake systems will be most affected by lowered water

levels, as would be the littoral zones of deep lakes. Low lake levels leave important fish habitat out of

the water, such as emergent vegetation and downed trees. Human disturbance and removal of this

habitat during times of low water could lead to permanent changes in ecosystem functioning. In

contrast, high water conditions could result in redistribution of substrate and structural features to

deeper water, and also uproot vegetation.

Seepage lakes are the most sensitive to changes in precipitation and groundwater elevations. A lake is

either surface- or groundwater- dominated, and its water chemistry is influenced by the relative

contribution of each. If the dominant water source shifts from precipitation and overland flow to

groundwater, it will shift from being a soft water to hard water lake. If on the other hand, groundwater

sources are reduced due to long-term declines in the water table, lake chemistry could become more

dependent on precipitation.

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Changes in water chemistry could have major implications for food webs, phytoplankton and

zooplankton communities, algal and rooted aquatic plant growth, as well as nutrient cycling and methyl

mercury production.

There are multiple social impacts of changes in lake levels including impacts on individuals who are

lakeshore property homeowners. Examples are loss of property to shoreline erosion through high

levels, or loss of recreational use through low water levels. There are also policy implications of long-

term changes in water levels, including pressure to redefine the “ordinary high water mark” which

determines the boundary between public waters and private property, or attempts to modify water

levels through augmentation, dams, or diversions.

RIVERS AND STREAMS The state’s thousands of miles of rivers and streams will also be affected by a changing climate. These

impacts include changes in baseflow, increased runoff with increased precipitation, changes to aquatic

habitats, and land use.

BASEFLOW Baseflow is the portion of streamflow from groundwater discharge. Data were collected by the U.S.

Geological Survey with 20 long-term stream gauges having at least 40 years of record. Analysis of these

data showed that all streams had a significant increase in baseflow after 1970 except a small area in

north central Wisconsin (Magnuson et al., 2003). We expect that trends in increased baseflows will

continue with the same pattern—increasing in parts of the state and decreasing in others, based on

WICCI projections of increased precipitation. Potential ET may offset the increase in precipitation.

Temperatures are expected to increase and increased potential evapotranspiration may occur requiring

additional need for irrigation from streams or groundwater. When groundwater levels decrease,

baseflow also decreases. Groundwater-fed streams, which may provide habitat for coldwater fish

species like trout, may be more profoundly affected.

RAINFALL AND RUNOFF Increases in winter and spring precipitation will likely cause increases in large runoff events, leading to

soil erosion, channel erosion, sediment and nutrient transport, increased eutrophication, habitat

degradation, and mobilization of sediment. Surface water quality is likely to decrease because of the

flush of runoff from bigger storms. Increased runoff will lead to flooding of small rivers and streams.

In some instances, flashy streams—those whose velocity increases dramatically with rainfall with drier

periods in between—will lead to a pulse of contamination that may have higher concentrations of

hazardous substances. Increased precipitation without cover crops can also lead to a change in habitat

by producing wider, shallower streams.

Changing rainfall patterns may impact flows on the Mississippi River and its tributaries. Large rivers in

general will be affected. On rivers like the Wisconsin River where power is generated through flow,

electrical generation may be impacted.

38

FISH HABITAT The WICCI Coldwater Fish and Fisheries Working Group has dealt with the effect of climate change in

detail. Some of the impacts include:

One- to two-years storm events may cause channel-forming flows, changing fish habitat

Coolwater fish habitat will change with rising water temperatures

Lower baseflow will decrease trout habitat, with fewer coldwater stream miles

THE BUILT ENVIRONMENT Large rainfall events will impact floodplains which will have impacts on the built world. Zoning codes

may need to change, and improvements to dams for safety precautions will need to be made.

Streams in urbanized areas are already stressed. An increase in precipitation will selectively degrade

watershed streams where a high percentage of land is impervious.

Where flows decrease and temperatures increase, waste assimilation capacity will change. This would

compromise wastewater treatment operations.

GROUNDWATER Climate change will affect groundwater resources across the state. However, given the diverse geologic

and hydrogeologic conditions present within the state, the nature of the change will be site-specific,

depending on soil and surficial material characteristics, topography, depth to bedrock, depth to

groundwater and land use practices. Climate change will have the most significant impacts on shallow

groundwater systems rather than deep groundwater systems such as those used by public water

systems in Dane County and in southeast Wisconsin.

The assumed changes in climate, notably increases in total annual precipitation, changes in the seasonal

distribution of precipitation and increased average temperature, all will affect the groundwater system.

Generally, the impacts will be manifested as changes in groundwater recharge which, in turn, will lead to

other water resource impacts. An increase in precipitation normally correlates with an increase in

recharge and ultimately a rise in elevation of the groundwater surface, although the magnitude of the

change in recharge and groundwater levels will not be uniform. However, concurrent increases in

temperature as a result of climate change and resultant changes in land use and water use patterns may

offset any increase in recharge, and certain areas of the state could actually experience declines in

groundwater levels. Due to the complexity of factors affecting the groundwater system, discussions of

anticipated impacts to the groundwater resources of the state as a result of climate change are highly

speculative and very general in nature.

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GROUNDWATER

RECHARGE Long–term forecasts predict

increased precipitation in fall,

winter and spring, but not in

summer. More frequent large

precipitation events, defined as

greater than 2 inches of rain in

a 24-hour period, are also

predicted. Since soil types and

surficial materials are not

consistent throughout the

state, the impacts to

groundwater of increased

precipitation will also not be

consistent. In areas where

groundwater recharge occurs

quickly, depth to groundwater

is normally fairly shallow and

there is little topographic relief.

Frequent high intensity storms

could cause groundwater levels

to rise above the ground

surface leading to flooding

conditions.

In southeast to south central

Wisconsin where soils are fine-

grained tills, the groundwater

table will rise faster than it will

in parts of the state where soils

are more permeable. If more

precipitation falls on low-lying

areas with porous soils, the

water table rise may top the

ground surface.

Areas with high groundwater

recharge rates are most

vulnerable to negative impacts

if these areas are developed

and are subject to prolonged

Case Study on Groundwater Flooding

In the summer of 2008, about 14 inches of rain fell in a 10-day period in southern Wisconsin, resulting not only in overflowing streambanks, but in groundwater flooding (figure 25). About 4,300 acres of land near Spring Green but not in the Wisconsin River floodplain became inundated with water—water that rose from the ground and overtopped the land surface. The land remained under water for more than five months. No amount of pumping would reduce the water level because there was no place for it to drain. Computer modeling and data from near-by monitoring wells showed that the groundwater level in the shallow aquifer had risen by as much as 12 feet. Residents in 28 homes left uninhabitatable moved out and received compensation from the government for the value of their homes. Scientists and policy-makers can use real-life extreme weather events like the Spring Green example to help predict where groundwater flooding may occur in other, geologically similar areas of the state. The Wisconsin Geological and Natural History Survey is conducting research that will apply a series of climate forecast and hydrologic models to selected landscapes that are vulnerable to water table rise and groundwater flooding.

Figure 25. Flooding in Spring Green in June 2008 was caused by

groundwater overtopping the land surface.

Photo by Madeline Gotkowitz

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dry cycles or drought. In some instances, the ground water table can rise as much as twelve feet in only

a few weeks given a significant amount of precipitation (see sidebar on previous page).

The impacts of flooding on humans can be great, including flooding of basements, homes, and septic

systems. This can lead to other environmental impacts if septic systems are near other surface waters

or sources of drinking water.

Additionally, changes in recharge lead to changes in the amount of groundwater that is discharged to

springs and other surface water features. Significant changes in recharge could result in dramatic

changes in the dynamics of lake, stream and wetland systems. Decreased recharge would result in

reduced flow from springs, lower baseflow in streams, loss of some wetlands and lower lake levels in

most lakes. On the other hand, an increase in recharge would produce the opposite effects and if taken

to an extreme could result in increased flooding and conversion of some wetland systems to lakes.

THERMAL IMPACTS ON GROUNDWATER Increased temperatures predicted by climate forecasters may also impact groundwater. Groundwater

recharge is largely dependent on the interplay between the amount of late season snowpack, the timing

of spring thaw and the timing of vegetative leaf-out, all of which are temperature-dependent. Climate

change forecasts call for increased winter precipitation, but due to the predicted warmer winter

temperatures, there is also greater likelihood that a higher percentage of the precipitation will fall as

rain, rather than snow. If significant rain events occur during the winter, when the surface materials are

frozen, much of the rain will run off the surface, entering streams and lakes, and will not contribute

significantly to groundwater recharge. However, warmer temperatures could also result in shorter

periods of frozen ground conditions leading to longer periods of time when the melting snowpack could

infiltrate and ultimately increase groundwater recharge.

During the summer months, climate forecasts suggest that temperature will increase but precipitation

will not change appreciably. Increased temperatures would lead to an increased length in the growing

season in Wisconsin and higher evapotranspiration during the summer and early fall months. If current

statewide cropping practices continue, a longer growing season without increased precipitation would

lead to increased reliance on irrigation systems, putting greater demand on groundwater resources.

Groundwater withdrawals by municipal water systems would also be expected to increase. In addition

to direct withdrawal of groundwater for irrigation and other summertime water uses, a longer growing

season also would result in a decrease in groundwater recharge because soils would not return to field

capacity until later in the year and soils would also begin to dry out earlier in the year, resulting in a

shorter effective period of recharge. All of these effects would lead to lower groundwater levels and

less groundwater discharge to surface waters, potentially leading to reduced summer flows in streams

and lower lake levels.

The longer growing season could also encourage more land to be put into agricultural use and therefore

more land area being subject to nutrient and pesticide applications. This could lead to increased risk of

contamination of both surface water and groundwater.

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As discussed above, if agricultural practices remain relatively constant, increase temperatures would

lead to a decrease in groundwater recharge. However, if practices are dramatically different, the

resultant impacts could also vary significantly. For example, if cropping patterns were to switch to more

drought-tolerant varieties, the reliance on groundwater would diminish and the impacts would be less

than presently projected. However, if development of biofuels using corn as a source were to expand,

additional acreage would likely be converted to growing corn, increasing the need for extensive

irrigation and ultimately leading to even greater adverse impacts to groundwater resources.

GROUNDWATER QUALITY Climate change also has the potential to affect the quality of groundwater through a number of different

mechanisms. Less recharge water could mean less dilution of contaminants and higher levels of total

dissolved solids in groundwater. In the situation where groundwater recharge occurs rapidly, a rising

water table will reduce the distance between land surface and groundwater, making the groundwater

more susceptible to contamination, from sources such as septic systems.

Higher winter temperatures and increased winter precipitation could result in more frequent icing

conditions on roadways leading to increased application of road salts. This would create greater

potential for contamination from chlorides of surface and groundwater.

Shallow groundwater is typically the same temperature as the mean annual air temperature. In shallow

wells, an increase in water temperatures could also lead to higher microbial activity, biofouling of wells

and an overall decrease in water quality.

Finally, an increased frequency in heavy precipitation events could lead to cascading water in open

boreholes. Improper filling of boreholes, used when drilling wells, is an easy source of groundwater

contamination. Water coming in through boreholes could lead to oxidation of sulfides, increased

microbial activity, increased sulfate (SO4), and release of arsenic and heavy metals.

WETLANDS Members of the Wisconsin Wetlands Association and other wetland specialists were instrumental in

identifying the major impacts of climate change on wetlands. Since climate forecasts show that

precipitation and temperature changes in the state are not uniform, the impacts of climate change on

Wisconsin’s wetlands will not be uniform across the state. In addition, the great natural variation across

wetland types also makes it difficult to generalize wetland impacts.

Response to climate change will vary between wetland types and geomorphic settings. Wetlands can be

located in groundwater discharge areas, such as slopes and springs, along shorelines, in low-lying

depressions, on former glacial lake beds, and throughout floodplains. 80 percent of Wisconsin’s

wetlands are directly adjacent to lakes, rivers or streams.

Another important consideration is that wetlands are dynamic in nature. Hydrology controls wetland

functions and wetlands are subject to fluctuating water levels over time. The plant composition, size,

and chemistry of wetlands change in response to extended wet and dry cycles and changes in hydrologic

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inputs (e.g., contributions from groundwater, surface water, and precipitation). Adjusting to these

ongoing natural disturbances is part of what makes wetlands some of the most productive and resilient

ecosystems on the globe.

These dynamics provide hints at how wetlands may respond to climate induced changes in precipitation,

temperatures, and extreme weather events; however, there are no long term data sets in Wisconsin

available to help quantify how wetland extent or functions have already responded to changes in

precipitation and temperature over time. Despite constraints, wetland ecologists can use their

knowledge of wetland structure and function to hypothesize on how certain wetland types or wetlands

in specific eco-regions may respond to changing hydrologic and temperature variables.

Potential impacts identified by wetland experts were similar in theme to those identified by lake and

river experts including: changes in hydrology; increased sediment and nutrient loads; proliferation of

invasive species; and shifts in plant, aquatic and animal communities. Participants also provided input

on potential impacts to Great Lakes coastal wetlands, and identified research needs.

CHANGES IN HYDROLOGY If winter and spring runoff increases, the area of some wetlands may increase, but there may also be a

shift to wetter, deeper wetland types. We can also expect to see an increase in flooding duration of

wetlands in low-lying areas. Ephemeral ponds will have higher initial water levels. Some will become

connected with other water bodies and fish will populate and prey on or compete with amphibians,

reducing their reproductive success.

Increased spring runoff may also increase stream bank erosion making stream channels wider and

deeper and they may become disconnected from wetland-rich floodplains. Incised streams will lose the

associated benefits of floodplain wetlands for sediment trapping, nutrient retention and aquatic habitat.

An increase in infiltration may enhance the extent of fens and other groundwater fed wetlands, but that

is dependent on timing of precipitation events. If winter rains are accompanied by a longer frost-free

period that could increase recharge and shift the water budget toward larger groundwater input. This

could benefit fens and saturated-soil wetlands. If winter rains fall on frozen ground however, winter

flooding could greatly increase delivery of pollutants to downstream wetlands, and result in little or no

recharge.

Responses to increased air temperatures will vary depending on the degree of groundwater inputs to

the wetland. Shallow wetlands could dry out earlier in the summer with greater evaporation and

warmer water. Wetlands with high levels of groundwater inputs are less likely to dry up from

evapotranspiration, but their size may decrease.

INCREASED SEDIMENT AND NUTRIENT LOADS Shifts in both temperature and precipitation will change the nutrient dynamics in wetlands. Increased

precipitation could cause some wetlands and hydric soils to release phosphorus, while methane

emissions may increase in others (e.g., sedge meadows in Southern Wisconsin). Increased summer

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drought and evapotranspiration will increase decomposition and change nutrient dynamics including

leading to an increase in CO2 emissions

Increases in precipitation will lead to increases in sedimentation downstream, particularly to wetlands

located in floodplains. Increased sedimentation could lead to lower wetland diversity which may alter

the wetland’s ability to clean water (positively or negatively). Increases in sedimentation may stabilize

carbon stored in wetland soils via carbon-mineral complexes which are relatively stable compared to

organic matter.

PROLIFERATION OF INVASIVE SPECIES: Increased spring and fall runoff and flooding may facilitate the spread of invasive species (e.g., Reed

Canary Grass and Japanese knotweed) along riparian corridors by dispersing more non-native seeds

throughout the landscape. Dispersal of native noxious species may also benefit. Reed canary grass may

increase in runoff-fed wetlands, but may decrease in kettle and pothole wetlands due to higher water

levels and longer periods of inundation. Spread of invasive species may also lead to subsequent

increases in sediment and nutrients in wetlands.

Increased water temperatures will allow more southern invasive species to proliferate in deep marshes

and aquatic bed wetlands. For example, Eurasian watermilfoil may increase in abundance as surface

water temperatures increase.

Best management practices for invasive species management may need to change in response to

changes in early season temperatures and wetter summers (e.g., Purple loosestrife biocontrol

effectiveness may decrease with wetter summers, requiring a change in the timing of control efforts).

SHIFTS IN PLANT, AQUATIC AND ANIMAL COMMUNITIES Many of the plant community and wildlife impacts discussed here are also being addressed by the plant

and the wildlife WICCI groups. Wetland plant communities are expected to shift with increasing

temperatures and increased or decreased precipitation. For example, plant species that are adapted to

cooler water temperatures can be expected to decrease with higher temperatures. Meadow and

shallow marsh wetlands will shift toward deep marshes with an increase in water availability. Floodplain

wetlands and ephemeral ponds could have longer periods of inundation and increased accessibility to

fish populations, with negative consequences for amphibian reproductive success.

Wetter winters combined with warmer growing seasons could cause a loss of northern type of wetlands,

such as bogs and conifer swamps. Northern forested wetlands may flood out due to enhanced summer

flooding or become more susceptible to disease. There may be reduced tree species regeneration with

increased flooding as even flood tolerant species require dry periods to become established. Wetter

growing seasons could lead to an increase in vertical heterogeneity in some herbaceous wetlands

through an increase in the formation of tussocks. Increases in invasive species will reduce wetlands’

wildlife value.

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The group also identified “pinch points” where heavy precipitation events, changes in water availability,

or warming temperatures will affect vulnerable wetlands and associated plants and wildlife. For

example, one heavy rainfall event could extirpate small isolated populations in glacial relict wetlands.

Deeper frost can cause greater mortality in hibernating animals. Extreme winter snowfall could affect

the winter survival of some species such as deer. In contrast, extreme summer droughts could have

negative impacts on some species and could provide competitive advantages for others.

Species mobility may also be impacted by climate change. Species with poor mobility may suffer local

extirpations and be unable to shift ranges north. This could be a cumulative negative impact. For

example, some wetland tree species may not be able to move fast enough to compete if climate zones

shift in a north-south direction.

Deer may increase browsing rates if winters are warmer. This could be catastrophic in areas of the state

where browsing pressure has already substantially reduced regeneration of vulnerable wetland species

such as Northern White Cedar and Eastern Hemlock. Increased temperatures may also increase

herbivory from insects and insect diversity, but we may see a loss of northern invertebrates.

GREAT LAKES COASTAL WETLANDS The prediction of increased temperature will affect coastal wetlands (Figure 26) in many ways. We may

see changes in the lower food web. For example, as temperature increases, there may be shifts in

phytoplankton communities which will impact the rest of the food web. Increased temperatures may

lead to decreases in plant diversity and fish communities. There will be a loss of boreal species.

It is also possible that a more temperate environment will lead to increased shoreline development.

There may be more wetland fill or wetland alteration for development. Additional loss of wetlands can

lead to increased eutrophication and sedimentation.

Figure 26. A coastal

wetland on Madeline

Island drains to Lake

Superior.

Photo by Carolyn Betz

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Decreased water levels in the Great Lakes would also have impacts on wetlands. If lake levels drop,

there may be a lakeward expansion of wetlands. Some of the early successional wetlands may be filled

with invasive species. Anadromous fish could be disconnected from streams. In some instances, coastal

wetlands may become disconnected from the Great Lakes through decreasing seiche activity.

Decreased water levels may place a greater demand on dredging navigational channels. On Lake

Superior, when water levels drop, some wetland sediments could become exposed, resulting in exposing

contaminated sediments in some of the toxic hotspot areas.

CHAPTER VI. INFORMATION GAPS – RESEARCH, INVENTORY

AND MONITORING NEEDS To make good water resource management and adaptation decisions in the face of a changing climate,

we need to have current and spatially explicit information about and understanding of hydrologic

processes, water levels and flows, and land and water uses, as well as the capacity to use and apply this

information using state-of-the art hydrologic modeling tools. Wisconsin is well positioned to take on this

challenge through existing partnerships and expertise at the US Geological Survey’s Water Science

Center, the UW Center for Limnology, the UW- Stevens Point Center for Watershed Science, the UW

Water Resources Institute, the Wisconsin Geological and Natural History Survey, the UW Milwaukee

WATER Institute, and the Wisconsin DNR.

However, the foundation of this understanding is a well-funded water resource monitoring network,

which is currently underfunded and driven by immediate resource management needs rather than long

term change. One of the objectives of the Water Resources Working Group is to help identify and

prioritize information gaps in this network, and to recommend both short term and long term research,

inventory, and monitoring needs to better understand the implications of a changing climate for

management of Wisconsin’s water resources.

MONITORING AND INVENTORY NEEDS A robust water monitoring network is imperative to be able to detect and track the impact of rising

temperatures and changes in precipitation on aquatic ecosystems, as well as to fully characterize the

variability of hydrologic processes, and develop appropriate models for developing adaptation

strategies. In addition, one of the necessary components of implementing a climate change adaptation

strategy is measuring the results of the chosen management activity. While most adaptation strategies

will be implemented on a decade-scale time frame, we must begin our inventory and monitoring

strategies as soon as possible. The WRWG has identified the following initial priorities for expansion or

improvement of our existing water resource monitoring and information capacity.

Develop a strategic framework for a climate-response water monitoring network, including stream

flows, lake levels and the shallow groundwater system, and dedicate state resources to maintain

this network over the long term.

Fill gaps in the state’s flow gaging network by updating and implement the flow-gaging

recommendations provided in “An Integrated Water-Monitoring Network for Wisconsin,” prepared

by the US Geological Survey in 1998 and updated for the Waters of Wisconsin effort in 2003.

We need to emphasize long-term data gathering and analysis as opposed to short-term,

project specific flow gaging.

It would be useful to re-activate discontinued flow gaging stations that were established

before 1950. Most of the state level climate and stream flow analysis has used 1950 to

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present flow gaging data, such as the analysis by Steve Greb presented in Chapter 3. The

analyses would be more robust if we had a more complete stream flow record. Discontinued

crest-stage gages should also be re-activated to help better determine if the magnitude of

frequent floods and bankfull discharge is changing.

Institute continuous stream temperature measurements at stations that are part of the National

Streamflow Information Program and also on representative small cold, cool and warm streams.

Water temperature changes are the most obvious impacts that a warming climate would

create. There are no long-term stream temperature records available to researchers, so we

need to begin collecting that data right now.

Establish a state-wide network of stations where scientists will record stream channel geometry

(bankfull width, depth and area), profile, sinuosity, bed forms and channel materials at recurring

intervals.

One of the most likely impacts to stream health is the change that will occur to the size and

shape of stream channels that result from changed precipitation patterns. The current

predictions are for more intensive precipitation events at longer intervals. As a result,

channel-forming flows (discharges in the 1.0-1.4 year recurrence interval) will occur more

frequently and we can expect channel widening and downcutting, both of which will reduce

aquatic habitat and contribute additional sediment to our stream systems.

Measure extent and impact of floods by delineating floodplains during flooding events and

determine how this is different from what we do now.

Enhance citizen-based monitoring efforts to include seasonal measurements such as ice off/on dates

for lakes, high water and low water thresholds, onset and length of lake stratification, and blue-

green algal bloom frequency.

Many of the changes to aquatic ecosystems involve changes in timing of key events, which are

difficult to capture using professionally designed and staffed monitoring programs. Citizens

who live on or near resources of interest can play a key role in documenting changes in timing,

frequency, duration, and magnitude of various hydrologic processes and aquatic ecosystem

change.

Establish regular surveys and assessment of aquatic vegetation on lakes, streams, and wetlands to

detect northward migration of key sentinel species, as well as non-native species that may move

into the state

We need to improve inventory and monitoring of wetland and aquatic plant species located at

the limit of their range. This should be a high priority because of the vulnerability of these

species and their utility for monitoring the progression of climate change effects.

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Build upon existing climate monitoring efforts to include parameters that are useful for

understanding hydrologic processes, such as direct evapotranspiration measurements, soil

moisture, frost depth, etc.

There is a need to update and improve existing wetland inventories to include the identification of

water source and provide a consistent state-wide inventory for all organizations to improve our

ability to estimate the potential impacts of climate change and develop adaptation strategies.

There are several wetland classification systems currently in use by a variety of organizations

in the state. The WI wetland inventory is commonly used but regulatory entities use “Wetland

Plants and Plant Communities of Minnesota and Wisconsin” while some organizations may

use other systems. While some systems provide for identifying water source (i.e.,

groundwater, transitional or surface), it is rarely determined, and yet this may be one of the

most important factors that determine whether a wetland is vulnerable to projected climate

changes.

The Water Resources Working Group will continue to collaborate with other WICCI working groups, such

as Forestry, Wildlife, Stormwater, Plants and Natural Communities, Coastal Communities, and Cold-

water Fisheries, to identify monitoring and information gaps of mutual interest and need.

RESEARCH NEEDS One of the first tasks of the WICCI Water Resources Working Group was to identify and prioritize

climate-related water resources research areas that should be explored using the new downscaled

WICCI data. Priorities were shaped by the Working Group over the past year, with input from other

water resource professionals at workshops sponsored by the Wisconsin Section of the American Water

Resources Association (AWRA), and the Wisconsin Wetlands Association (WWA). The following research

areas were identified:

Enhancing or refining existing hydrologic models to address:

Geochemical responses to climate change

Implications for lake levels, stream flows and groundwater recharge

Linkages between climate and ecological models

Improvement of water-resources model parameters most sensitive to climate change

Development of soil frost and the effect on groundwater recharge and surface runoff

Wetland hydrology

Improving predictive models of snow depths, frost depths, and a better understanding of whether precipitation will come as rain or snow

Compiling and analyzing spatial/temporal trends in long-term hydrologic information (e.g., statewide stream gauging, groundwater levels, lake water temperature, water clarity, etc.)

Compiling and analyzing hydrologic parameters that are used by managers and regulators that may be affected by climate change (e.g., ordinary high water mark, Q7,10 flow statistics, wetland

50

delineation guidelines, 100-year flood frequency interval, etc., hydrologic risk analysis for infrastructure design)

Initiating the design of a climate response monitoring network (water levels and flows monitoring approach, critical ecological-flow thresholds)

Linking physical/hydrodynamic responses of lakes to climate change

Linking thermal impacts to lakes and streams and the effects on biological communities and/or nutrient and carbon cycling

Developing innovative outreach or education projects that address climate change and Wisconsin’s water resources

Evaluating costs and benefits of adaptation strategies related to water-resource management

Investigating the effects of rapidly rising water temperatures in the Great Lakes (esp. Lake Superior) and how this will affect wetlands, algal blooms, seiche effect and mixing

Better understanding of links between coastal processes and coastal wetlands, such as seiches and nearshore bathymetry, as well as erosion

The working group’s list of research needs was incorporated into two calls for research in the University

of Wisconsin System in late 2009 that included:

1) The UW System’s portion of the Wisconsin Groundwater Research and Monitoring Program’s

(WGRMP) call for proposals, a collaborative effort led by the state’s Groundwater Coordinating

Council; and

2) A new UW Water Resources Institute solicitation for water resources research in support of

understanding climate change impacts and adaptation

GROUNDWATER RESEARCH AND MONITORING PROGRAM Objectives for applications for the UW System funds distributed through this solicitation are determined

by the Groundwater Research Advisory Council (GRAC). With the advice of the WRWG, three main

objectives were amended to contain the following climate-related groundwater issues:

Objective A: Maintain or enhance groundwater quantity • Effects of climate change and variability on groundwater levels, flow patterns, and quantity.

Objective B: Maintain or enhance groundwater quality

Effects of climate change and variability on groundwater quality.

Develop strategies for ensuring high quality groundwater in the face of climate change.

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Objective C: Maintain or enhance groundwater management

Investigations into the best methods for optimizing groundwater use for human and

environmental needs in Wisconsin, including strategies for long-term management.

Implications of climate change on groundwater management.

UW-WRI CLIMATE IMPACTS SOLICITATION A second task of our group was to provide a set of research priorities for the UW Water Resources

Institute’s call for proposals using base research funding from the U.S. Geological Survey through its

104B National Water Resources Institute Program. The UW-WRI dedicated its research funding for 2010

and a number of future years, to water resources research in support of the WICCI effort.

FUNDED PROJECTS Calls for proposals for both UW-WRI and for the WGRMP were released through the state’s Joint

Solicitation on October 28, 2009. Full proposals were sent out to external peer review and discussed

and ranked by separate research advisory committees convened by WRI in January 2010. The following

projects were selected for funding in 2010-2011 through WRI:

Development and application of a user-friendly interface for predicting climate change induced changes in evapotranspiration Principal Investigator: Steven Loheide (UW-Madison) The abstract can be found at http://wri.wisc.edu/Default.aspx?tabid=69&ctl=Details&mid=514&ProjectID=98562405 Response of Ice Cover, Lake Level and Thermal Structure to Climate Change in Wisconsin Lakes Principal Investigator: Chin Wu (UW-Madison) The abstract can be found at http://wri.wisc.edu/Default.aspx?tabid=69&ctl=Details&mid=514&ProjectID=98562404

Through the WGRMP, the Wisconsin Department of Natural Resources also funded the following

research project:

Information Support for Groundwater Management in the Wisconsin Central Sands

Principal Investigators: George Kraft and David Mechenich (UW-Stevens Point) http://www.dnr.state.wi.us/org/water/dwg/gcc/rtl/2010/FY11Projects.pdf

Finally, a previous project funded through the Water Resources Institute is directed at understanding

climate change impacts:

Forecasting Impacts of Extreme Precipitation Events on Wisconsin’s Groundwater Levels Principal Investigator: Madeline Gotkowitz, Wisconsin Geological and Natural History Survey http://wri.wisc.edu/Default.aspx?tabid=91&ctl=Details&mid=397&ProjectID=98562368

ONGOING AND CURRENT RESEARCH A variety of other research projects investigating the impact of climate change on water resources and

hydrologic processes are already underway in Wisconsin.

CHAPTER VII. ADAPTATION STRATEGIES FOR WATER

RESOURCES

GOALS OF ADAPTATION FOR WATER RESOURCES To provide a framework for thinking about adaptation from a water resources management perspective,

it is important to articulate what the overall goals of adaptation might be, either at the statewide level

or at the local level (municipality or watershed). The following goals were developed by the WDNR’s

Water Division and help describe what our Water Resources Working Group is striving for in developing

adaptation strategies.

Minimize threats to public health and safety by anticipating and managing for extreme events--floods and droughts We cannot know when and where the next flooding event will occur, or forecast drought conditions

beyond a few months, but we do know that these extreme events may become more frequent in

Wisconsin in the face of climate change. Therefore planning for and being prepared to deal with

extreme events more effectively should be an adaptation priority.

Increase resiliency of aquatic ecosystems to buffer the impacts of future climate changes by restoring or simulating natural processes, ensuring adequate habitat availability, and limiting population level impacts of human activities. A more extreme and variable climate (both temperature and precipitation), may mean a shift in how

we manage aquatic ecosystems. We need to try to absorb or accommodate the changes rather than

try to resist them. For example, we may want to restore historic (pre-development) seasonal water

level fluctuations in lentic and lotic environments through water level regulation (dam operation),

appropriate groundwater and surface water withdrawals, and restore or reconnect floodplains and

wetlands, as well as maintain or provide migration corridors for fish and other aquatic organisms.

Stabilize future variations in water quantity and availability by managing water as an integrated resource (by “keeping water local”) and supporting sustainable & efficient water use. Many of our water management decisions are made under separate rules, statutory authorities,

administrative frameworks, and even different government entities. This can leading to conflicting

and inconsistent outcomes. In the face of climate change, the more we can do to integrate these

decisions, and at the appropriate geographic scale (aquifer, watershed), the better adapted and

ready for change we will be. In addition, treating our water as a finite resource, and knowing that

supply will not always match up with demand will allow for more sustainable water use in the

future.

Maintain, improve, or restore water quality under a changing climate regime by promoting actions to reduce nutrient and sediment loading. Water quality initiatives will need to be redoubled under a changing climate, in order to minimize

worse-case scenarios (e.g. fish kills, harmful blue-green algae blooms, mobilization of contaminated

sediments, etc.) and prevent exacerbation of existing problems.

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Many of these goals are not “new” to climate change, and reflect ongoing priorities and concepts that

guide our water resource management programs in Wisconsin. However, climate change gives new

emphasis and priority to these issues, and perhaps can be used to leverage additional resources to

implement the needed strategies.

OTHER ADAPTATION CONCEPTS A few other concepts or guidelines should be considered in developing adaptation strategies for water

resources management:

Modify expectations – Often society is conditioned to expect that water resources (lake levels, stream flows, wetlands, groundwater levels) should be static, or at least only vary slightly around a long term average. For example, lake property owners become alarmed if lake levels are slightly higher or lower than average, or stay at an abnormally high or low level for more than a season. With climate change, we may need to shift our expectations of what is “normal” and expect more variability or even a different standard of “average” or normalcy.

Incorporate dynamics and flexibility into decision-making (adaptive management) – Many water-

related infrastructure, planning, and permit decisions are based on long-term average historical conditions, and are expected to last for decadal or indefinite time horizons. With shifting baselines and more variability, water management decisions will need to become more “adaptable” to allow for review and modification with real-time water-related information.

Improve capacity to detect trends and thresholds (leads to better decisions) –To manage water

adaptively, we need to have good, up-to-date information on water levels and flows, water quality,

and projected water use and demands at a temporal and spatial resolution adequate enough to

detect patterns, trends and thresholds. Supporting a robust statewide water monitoring system will

be critical in this regard (see the monitoring needs identified in Chapter 6).

Address impacts and adaptation at local levels as much as possible -- Because of the variability of

climate projections in different parts of the state, as well as differences in topography, soils, land

cover, land use, and resulting hydrologic processes, effective adaptation strategies will be best if

they are developed at relatively local scales (watersheds, drainage basins, catchments, etc). In

addition, we need to plan for and implementation these strategies by involving the various

stakeholder groups and appropriate management entities within that watershed or catchment.

Discussion about management implications -- To frame a discussion about how to develop

adaptation strategies, we discussed the following issues:

Who is it that needs to develop policies, management strategies, or holds regulatory authority

to make the changes that are needed?

How will management decisions be carried out?

At what level are these strategies best delivered? Some can only be carried out at a statewide

level, such as the development of nutrient standards. Others are local decisions, such as

infrastructure or land use planning

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IMPACTS AND ADAPTATION STRATEGIES To begin addressing adaptation strategies for water resource impacts of climate change, we asked

attendees at two WICCI Working Group sponsored workshops to brainstorm ideas for some of the major

impacts that had previously been identified. We asked participants to think about the scale and

timeframe for the strategy, as well as who would implement them and any potential obstacles or

barriers.

The following list should not be considered a thorough analysis or set of prioritized recommendations,

but rather is meant to illustrate the breadth and scope of the types of strategies that will need to be

developed at multiple levels in order to deal with the consequences of climate change to Wisconsin’s

water resources.

Increased flooding will have impacts on infrastructure and agricultural land

Adaptation Strategy: Identify and map Potentially Restorable Wetlands (PRWs) in floodplain areas

Who: WDNR, local land management agencies, NRCS

Scale: Watershed-based, flood prone areas

Timeframe: Ongoing

Obstacles: Education, cost, tax code, incentives to use land for other purposes; misconceptions about wetlands

Adaptation Strategy: Reverse the loss of wetlands and restore prior-converted wetlands in upland

areas to provide storage and filtration and mitigate storm flows and nutrient loading downstream

Who: WDOT, Landowners, state and fed agencies (NRCS)

Scale: Watershed scale

Timeframe: Ongoing, long term

Obstacles: Education, cost, tax code, incentives to use land for other purposes; misconceptions about wetlands

Harmful blue-green algal blooms will occur more frequently with increased summer temperatures Adaptation Strategy: Increased monitoring of inland beaches for blue-green algal toxins

Who: Local health departments and lake organizations

Scale: Statewide, but prioritize beaches where monitoring is not occurring and potential is increasing (e.g. shallow, meso- to eutrophic northern lakes)

Timeframe: Short-term, problem identification; long-term, stable monitoring network

Obstacles: lack of funding, awareness at local level and in some parts of state Adaptation Strategy: Develop statewide standards for blue-green algal toxins

Who: WDNR, State Legislature

Scale: Statewide

Timeframe: Longer term

Obstacles: statutory change, political will, lack of understanding about blue-green toxicity

Groundwater extraction and demand for water will increase due to variable precipitation projections and warmer growing season temperatures Adaptation Strategy: Encourage large water users to locate in areas with adequate (sustainable) water sources, such as near large rivers or the Great Lakes

Who: State – Regional water management authorities

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Scale: Aquifer/regional (Groundwater Management Areas)

Timeframe: Immediate need in some areas; Long-term planning

Obstacles: Competing demands; reasonable use doctrine; economic constraints; public opinion

Adaptation Strategy: Encourage water conservation (rural and urban) through incentives and regulation

Who: State, counties, and municipal government

Scale: Statewide

Timeframe: Short-term – Great Lakes compact requirement

Obstacles: Public/private water users; rate structures that do not reward conservation; need to place cost/value on agricultural water consumption

Adaptation Strategy: Promote Integrated Water Management: Planning water use based on long term projections of supply and demand and tied to land use and economic growth forecasts

Who: Regional planning agencies

Scale: Aquifer/watershed

Timeframe: Ongoing

Obstacles: Cost, availability of information in some areas

Seepage lake levels will changes due to variable precipitation, recharge, or increased ET. There additional implications for water chemistry, habitat, and shorelines Adaptation Strategy: Enhance and restore shoreline habitat (coarse wood, littoral and riparian vegetation, bio-engineered erosion control) to withstand variations in water levels.

Who: Lake associations, property owners, DNR/USFS managers

Scale: Statewide – seepage lakes

Timeframe: Long term

Obstacles: Limited resources, people Adaptation Strategy: Aquifer augmentation/injections to keep water in basin (or diversions if water is too high)

Who: Select communities – water utilities

Scale: Localized

Timeframe: Long term

Obstacles: Existing regulations regarding interbasin transfers, potential for contamination of water supply, cost, public perception

Adaptation Strategy: If aquifer is low, enhance infiltration by reducing impervious surfaces in urban/riparian areas and changing land management practices (e.g. agriculture to forestry)

Who: Local units of government; landowners; management agencies/developers

Scale: Statewide

Timeframe: Ongoing

Obstacles: Cost, awareness/education, scientific uncertainty about land cover impacts to hydrology

Adaptation Strategy: Account for changes in water levels in planning and zoning standards for lakeshore development

Who: County level implementation, but statewide standards needed

Scale: Statewide

Timeframe: Ongoing

Obstacles: Cost, politics, public will, awareness, education

57

Adaptation Strategy: Adjust and modify expectations and uses, especially of seepage lakes; recognize that some lakes may not be suited for all uses such as recreational boating in shallow waters

Who: Lakeshore owners, Lakes Partnership; agencies

Scale: Statewide

Timeframe: Ongoing

Obstacles: Riparian rights, education, need, realtors

Increased sediment and nutrient loading due to earlier and more intense spring runoff events Adaptation Strategy: Resize manure storage facilities, wastewater facilities, storm sewers, infrastructure to accommodate increased storm flows

Who: Resource management agencies, local government, industry

Scale: Statewide; Midwest regional issue

Timeframe: Ongoing – short term (immediate need)

Obstacles: Cost, changing regulations, research, new statistical models Adaptation Strategy: Reverse the loss of wetlands, restore prior-converted wetlands to provide storage and filtration – mitigate storm flows and nutrient loading

Who: DOT, Landowners, state and fed agencies (NRCS)

Scale: Watershed scale

Timeframe: Ongoing, long term

Obstacles: Education, cost, tax code, incentives to use land for other purposes; misconceptions about wetlands

Adaptation Strategy: Protect recharge/infiltration areas, riparian buffers

Who: Local governments, landowners, urban dwellers

Scale: Watershed-based

Timeframe: Ongoing, long term

Obstacles: Education, need, identifying area, private property rights, regulations Adaptation Strategy: Incorporate water management strategies based on climate projections into farm-based nutrient management planning

Who: Farmer/landowner/county/DATCP/NRCS

Scale: Local, watershed implementation but statewide need

Timeframe: Immediate need - ongoing, longer term priority

Obstacles: Cost, weak regulations, property rights, current land uses and incentives for crop yields, lack of information for planners

Increased spread of aquatic invasive species due to changes in hydrology, water temperatures, and

warmer winter condition Adaptation Strategy: We did not develop adaptation strategies for this impact for this report. Since this is a first draft working document, we know that additional adaptation strategies will be developed, evaluated and refined over the coming years, including a strategy for aquatic invasive species.

REFERENCES CITED

Bates, B.C., Z.W. Kundzewicz, S. Wu and J.P. Palutikof, Eds. (2008). Climate Change and Water. Technical

Paper of the Intergovernmental Panel on Climate Change, IPCC Secretariat, Geneva, 210 pp.

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APPENDIX A. WATER RESOURCES WORKING GROUP

CHARTER

This charter outlines the purpose and function of the Water Resources Working Group, which is a part of

the Wisconsin Initiative on Climate Change Impacts (WICCI).

MISSION The Water Resources Working Group will assess and synthesize climate change impacts to Wisconsin’s

water resources and assist in the development of adaptation strategies for dealing with those impacts.

GOALS AND OBJECTIVES The Water Resources Working Group will:

Synthesize existing knowledge about potential changes in climate and their effect on Wisconsin’s water resources and identify gaps.

Produce an inventory of existing climate change research related to water resources in the state in relation to WICCI working group needs.

Identify and propose research and monitoring priorities concerning climate change impacts on water resources, with an initial focus on hydrologic processes (water levels and flows, groundwater/surface water interactions, watershed hydrologic budgets, etc).

Identify and seek appropriate funding to carry out priority research.

Obtain climate change predictions or scenarios specific for Wisconsin from the Climate Working Group, updated climate change predictions will be obtained as they become available, and made available to other hydrologic researchers.

Develop potential impact scenarios based on climate predictions for representative Wisconsin watersheds, aquifers, landscapes, and regions.

Develop adaptation strategies and guidelines for managing watersheds, aquifers, and water-rich landscapes that may be affected by changes in climate.

Suggest water monitoring strategies to better track and respond to changes in climate and enable informed decisions

WORKING GROUP PARTICIPANTS The participants of the working group are listed on the official WICCI Web site. The Water Resources Working Group will primarily focus on understanding the implications of changing

climate for inland water levels and flows, including lakes, rivers, wetlands, stream baseflows, and

groundwater.

DURATION OF WORKING GROUP The Water Resources Working Group has no set duration. The composition of the Group may change as

the interests of the Group participants and the Group’s activities change over time. The charter will be

reviewed on an annual basis in order to reflect any changes in Group participants and activities.

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DELIVERABLES The working group will be responsible for the delivery of the following:

Compilation of existing research and list of priority research needs related to hydrologic processes and climate change in Wisconsin

Statewide maps and/or GIS coverages identifying spatial variations in the direction and magnitude of key hydrologic processes that may be affected by climate change

Aid in development of watershed scale hydrologic models for climate change scenarios for representative regions of Wisconsin

Recommendations for adaptation strategies that could be applied at the statewide, basin, or local scale

(more to be worked out by working group)

CRITICAL DEPENDENCIES The success of the Water Resources Working Group will be closely related to the success of other groups

within WICCI, including:

Climate Working Group

Stormwater Working Group

Coldwater Fish and Fisheries Working Group

Central Sands Hydrology Working Group

Green Bay Working Group

Milwaukee Working Group

Aquatic Species/Ecosystems Sub-group of the Wildlife Working Group

Coastal Communities Working Group

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APPENDIX B. HISTORIC TRENDS IN FLOWS OF WISCONSIN’S RIVERS

AND STREAMS

METHODS US Geological Survey daily flow records (http://waterdata.usgs.gov/wi/nwis/sw) were the basis of the

trends analysis work for Wisconsin’s rivers and streams. Using the website’s search tool, 48 stations

which had complete or nearly complete flow records from 1950 through 2006 were used. Small data

gaps (< 5 percent of total record) were allowed in the 57 year time period studied, maximizing the

number of stations utilized while not compromising record completeness.

Annualized values for each of four metrics were chosen to examine trends. The metrics were

Annual Mean Flow -- Daily flows averaged over each year

Total baseflow- Annual values estimated from a baseflow separation program (Wahl and Wahl, 1995)

Annual Maximum Flow - One day maximum flow for each year,

Julian day center of flow volume -- The day that half the cumulative flow volume from January to May passes the station. This metric is a measure of the timing of spring runoff and is an indication of whether spring runoff is occurring earlier or later in the year.

Using statewide gridded precipitation values from Kucharic et al. (2010), total annual precipitation was

calculated for each year of every drainage basin corresponding to the USGS stations. Initial trend

analyses were carried out using the Kendall test (sometimes called the Mann-Kendall test). This

nonparametric test does not assume the observations arise from any particular distribution, but it does

assume that they are independent. Observations collected sequentially in time may not be

independent, but may exhibit autocorrelation (observations close together in time may either be more

or less similar than those further apart). This lack of independence can lead to biased estimates of

standard errors and test statistics.

Because there is no easy way to test for autocorrelation in the context of the Kendall test, linear

regression (regression of flow on year) as an alternative method was used to estimate trend and

examined the residuals from the regression model for autocorrelation. SAS® PROC AUTOREG was used

to test for autocorrelation because it automates this procedure for several response variables and many

separate streams. The procedure involved testing for autocorrelation using the generalized Durbin-

Watson statistic. This can be used to test for autocorrelation at any specified lag. The SAS procedure

included a backwards stepwise feature which allowed us to determine the appropriate order of the

autocorrelation model (i.e., whether autocorrelation was significant at lag 1, at lag 2, etc.). A linear

regression model was then fit with autoregressive errors (using the selected autoregressive order) and

the results examined. Using this approach, one can determine when there is evidence for

autocorrelation, and how the results are affected when we account for the autocorrelation.

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RESULTS The majority of the 48 stations showed neither a positive nor negative significant trend (p<0.10) for

three of the four metrics tested: annual mean flow, annual maximum flow, and center of flow day (see

Table 1). The fourth metric, baseflow, exhibited a positive trend at over half of the stations.

Interestingly, for all metrics, those stations that indicated trends tended to be highly skewed, either

positively or negatively, depending on the metric. For example, 85 percent of stations that showed a

significant trend in mean flow were in the same direction (positive). Similar patterns were seen for the

other metrics: 92 percent for baseflow (positive), 89 percent (negative) for one-day maximum, and 76

percent (negative) for center of flow day. The fact that the trends tend to be grouped in the same

direction, either positively or negatively, suggests the these flow characteristics have a common

environmental driver, such as precipitation, and the environmental driver(s) are affecting the flow

regionally in similar manner.

Values in parentheses in Table 1 indicate the number of regressive models that contained a significant

autoregressive parameter. Autoregressive components were found to be important in both the annual

mean and baseflow metrics. For example, flow in year (x) was influenced by the flow in the previous

year(s). Lag years between one and 15 were considered. From a physical perspective, the inclusion of

this autoregressive component seems reasonable for both metrics; i.e. above-average flow years

generally followed wet years; conversely drought years can extend their influence into subsequent

years, especially groundwater recharge and the affected baseflow. The lack of influence of

autoregressive parameters on one-day maximum flow is understandable because the ability of a single

day event to influence a subsequent year single day event is improbable. Similarly, the metric Julian day

center of flow is most likely influenced by spring temperature conditions, not precipitation.

Consequently, one would not expect these values to be autocorrelative; the timing of spring runoff one

year is not expected to influence the timing of runoff the following year.

Table 1. Number of stations exhibiting trends in a 57-year data set. Values in parentheses are the number of models that included autoregressive parameter. 48 stations were observed.

Metric

Trends

Increase Decrease Non-Significant

Annual mean flow 12(12) 2(2) 34

Baseflow 25(25) 2(2) 21

One-day max flow 2(2) 17(2) 29

Julian day center of spring

flow 5(2) 16(2) 27

The geographic locations of stations where significant trends were found are plotted in Figure 1

(a-d) for the four metrics examined. Stations with significant trends do not appear to be

randomly distributed across the state but have spatial patterns. This is particularly true for the

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annual mean and baseflow, where upward trends were seen in the southern and western part

of the state and downward trends were seen across the northern tier of stations.

Conversely, the one-day maximum and center of flow day stations with significant trends tend

to be evenly distributed across the state, with the exception of a small cluster in the southwest

for the center of flow metric. Again, there two metrics are influenced by annual precipitation to

a lesser extent than the mean and baseflow metrics. To graphically examine the influence that

changes in annual precipitation has played in these trends, each of the plots in Figure 1 was

overlaid with the spatial change in precipitation for the same time period (Kucharic et al.,

2010). General spatial agreement was observed between changes in precipitation and two of

the metrics: annual mean and baseflow. These two metrics are presented in Figure 2(a-b). Note

that the areas in yellow-red in the southern and western region of the state, corresponding to

the areas with greatest precipitation increases, are also where we observed a concentration of

stations with significant increases in mean and baseflow.

67

Figure 1 (a-d). Location of stations exhibiting significant trends of a) annual mean, b) low flow, c) one-day

maximum, and d) center of flow.

68

R2 = 0.4393

0

50

100

150

200

250

300

350

400

450

500

200 400 600 800 1000 1200

Precip(mm)

Flo

w(m

m)

Figure 2. Annual mean and baseflow overlaid on precipitation changes during the same time period (1950-2006).

(Maps prepared by Eric Erdmann, DNR, 2010)

To further examine the relationship between precipitation and hydrologic metrics, annual

precipitation depth and total precipitation volume was calculated for each of the stations’

catchments. These precipitation measures were obtained by summing the gridded monthly

precipitation data from Kucharik et al. (2010) for years 1950-2006 for points within the

delineated watersheds. If the mean annual flow is plotted against precipitation for each station,

a strong relationship can be observed (Figure 3). For all stations, the r2 ranged from 0.30 to

0.65. Stated otherwise, the precipitation explained between 30 to 65 percent of the variability

seen in mean flow patterns. Conversely, the remaining 35 to 70 percent is not explained by

precipitation and can be attributed to a variety of influences including changes in land use,

conservation practices, temperature, evapotranspiration, and groundwater withdrawals.

Figure 3. Annual precipitation vs. annual

flow for the Sheboygan R. at Sheboygan

(USGS Station no. 4086000)

69

Baseflow index (BFI), the ratio of annual baseflow volume to annual total flow volume, was

calculated for each year for each station. Surprisingly, half of the 48 stations showed a

significant increase in BFI. BFIs would be expected to decrease with increased precipitation

since more precipitation results in a greater percentage of runoff. However, a large number of

stations displayed an increase in BFI even though precipitation has generally increased in the

state. This suggests that factors such as land use may have more of an overriding influence

over the precipitation increase. Proper land use practices that promote infiltration have more

than compensated for the increased precipitation and resulted in a greater percentage of total

flow comprised of baseflow.

CONCLUSION Trends in flow over the past 57 years were determined for 48 USGS stations across the state of

Wisconsin. Four annual metrics (mean flow, baseflow, one-day maximum flow, and Julian day

of center of spring flow) were tested for trends using the non-parametric Kendall test as well as

linear regression, incorporating an autoregressive parameter. For three of the four metrics

(mean, one-day maximum, and Julian day center of flow) the majority of stations did not exhibit

a trend. Of the stations that did exhibit trends, the majority of them were positive for the mean

and baseflow metrics, and negative for the one-day maximum and center of flow metrics.

Autocorrelation played a strong role in the mean and baseflow time series, suggesting that the

prior year’s flow influences current year flow. Stations having significant trends in mean and

baseflow were not randomly distributed throughout the state but were generally correlated

with precipitation patterns. Less precipitation influence was observed with one-day maximum

and center of flow metrics. Calculated baseflow index values trended upwards at a majority of

sites, suggesting land use practices are strongly influencing flow regimes through increasing the

proportion of total flow as infiltration.

During the 57-year study period, statewide precipitation increased approximately 10-15

percent. Interestingly, the average statewide (based on the 48 stations) percent change in

annual flows observed over this same 57-year period was a comparable 14 percent, pointing to

the strong coupling between basin precipitation and river flow. Future annual precipitation

projections for the next half century, though quite variable depending on the climate model,

average in the 2 to 7 percent increase range. Thus, the increases in precipitation we’ve seen

over the past half century are equal to, if not greater than projected precipitation changes. Will

this translate into a corresponding change (2 to 7 percent) in annual flow for the State?

Possibly, provided other conditions remain constant, but seasonal precipitation patterns and

extreme events are also expected to change, which could impact runoff amounts and

consequent flows. In addition, temperatures are projected to increase, which will increase

evaporation potential and decrease water yield to the receiving waters. Finally, land use

changes, both rural and urban, will influence water cycle components (i.e. groundwater,

70

infiltration) and resultant river flows. Therefore, given that annual flow characteristics are a

product of multiple factors, it is difficult to predict changes in future flows. Hydrologic

modeling on a basin scale , which simulate these dynamic hydrologic processes and account for

changing land use conditions, temperature regimes, precipitation timing and characteristics,

are needed to fully understand the impact of future climatic conditions on Wisconsin’s river and

stream flow regimes.

REFERENCES Kucharik, C. J., Serbin, S. P., Vavrus, S., Hopkins, E. J., & Motew, M. M. (2010). Patterns of climate change

across Wisconsin from 1950 to 2006. Physical Geography, 31(1)

Wahl, K.L. and T.L.Wahl (1995). Determining the flow of Comal Springs at New Braunfels, Texas. In:

Texas Water ’95. San Antonio, TX Aug. 16-17, 1995, pp. 77-86.

71