Advisory Committee Meetingsantarosaplaingroundwater.org/wp-content/uploads/... · 7/13/2020 ·...

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Advisory Committee MeetingJULY 13, 2020

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Welcome, Introductions, and Agenda Review

Time Agenda Item Materials

3:00 Welcome, Introductions and Agenda ReviewBob Anderson, Advisory Committee Chairman Sam Magill, Advisory Committee Meeting Facilitator

N/A

3:05 General Public CommentsThis time is reserved for the public to address the Committee about matters NOT on the agenda and within the jurisdiction of the Committee.

N/A

3:10 Agenda Review & 2020 Meeting Schedule ReviewBob Anderson, Advisory Committee Chairman Sam Magill, Advisory Committee Meeting Facilitator

Agenda; June 22 Meeting Summary; 2020 Meeting Schedule

3:15 Historical and Current Water Budget and Model Update SummaryAndy Rich, Technical Staff

Update on model development Overview of water budget assumptions Discussion of water budget application to SMCs

Objective: Review and discuss water budget and model, and their application to SMCs.

Draft Historical and Current Water Budget/Model Update Summary; Budget Section; Summary Appendix

4:30 Sustainable Management Criteria ProposalsMarcus Trotta, Technical Staff

Review Modifications to Subsidence SMC Water Quality Degradation: Update on input received and next steps

Objective: Review and discuss SMC proposals and discuss additional considerations and next steps.

N/A

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Welcome, Introductions, and Agenda Review (continued)

Time Agenda Item Material 5:15 Updates (Time Permitting)

Marcus Trotta, Technical Staff Projects and Management Actions Grants Update Practitioner Workgroups Monitoring Network

Andrea Rodriguez, Outreach Staff Public Outreach Progress Update

Objective: Provide relevant updates that inform the Advisory Committee - AC to ask questions if needed.

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5:25 Review Meeting Action Items and Discuss July Meeting AgendasSam Magill, Advisory Committee Meeting Facilitator

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5:30 Meeting AdjournsUpcoming Community Workshop: Wednesday, July 29, 2020, 5:30-7:00pm Next GSA Board Meeting: Thursday, August 13, 2020, 1:00-3:30pmNext Advisory Committee meeting: Monday, September 14, 2020, 3:00 – 5:30 pm

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General Public CommentsThis time is reserved for the public to address the Committee about matters NOT on the agenda and within the jurisdiction of the Committee.


Agenda Review & 2020 Meeting Schedule ReviewMaterials: Agenda; June 22 Meeting Summary; 2020 Meeting Schedule


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Santa Rosa Groundwater Sustainability AgencyBoard and Advisory Committee Meeting Schedule

Historical and Current Water Budget and Model Update SummaryObjective: Review and discuss water budget and model, and their application to SMCs.

Materials: Draft Historical and Current Water Budget/Model Update Summary; Budget Section; Summary Appendix

Andy Rich, Technical Staff

Update on model development

Overview of water budget assumptions

Discussion of water budget application to SMCs


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Santa Rosa Plain Hydrologic Model –Updated Water Budgets

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Presentation Overview/Modeling Status

•Reminder: General Water Budget Components and SGMA Requirements•Santa Rosa Plain Hydrologic Model (SRPHM)

• Simulation processes necessary for water budget calculations• Revised model: calibration verification• Revised surface water and groundwater budgets• Introduction to watershed budget • Overview of approach to projected water budgets development

•Next steps• Development of projected water budgets


Quick Reminder: SGMA Water Budgets

CA CCR §354.18 & Best Management Practices document

Three water budgets for GSP:1. Historical conditions 2. Current conditions3. Projected conditions over the 50-year planning and implementation horizon

Water budget must include:◦ Inventory of all inflows (supply) and outflows (demand)◦ Summary of both surface water and groundwater budgets◦ Evaluation of changes of groundwater in storage◦ Estimation of groundwater overdraft (if applicable)◦ Estimation of sustainable yield

Water Budgets – Time Periods


Time Period

Proposed Date Range Water Year Types Represented in Time Period

Historical water years 1976 to 2018 Very dry: 1Dry: 7Normal: 20Wet: 13Very wet: 2

Current water years 2012 to 2018 Very dry: 0Dry: 2Normal: 4Wet: 1Very wet: 0

Water Budget Diagram

From: Water Budget BMP, California Department of Water Resources, 2016

SRPHM Integrated Simulated Processes Provide Detailed Water Budget Estimates


SRPHM Simulation Boundary


SRPHM Calibration Assessment –Simulated Groundwater Hydrographs


SRPHM Calibration Assessment – Water Levels


For Groundwater levels, model remains well-calibrated.Simulated waterlevels are on average greater in SRPHM1.0+ than SRPHM1.0. Root mean square error increased by 0.9 ft from SRPHM1.0 to SRPHM1.0+, though median waterlevel residuals did not change (=-7.2 ft).

SRPHM Calibration Assessment – Streamflows

7/21/2020 santarosaplaingroundwater.org 1

Original Plots from 7/13/2020 with mistake in unit conversions

SRPHM Calibration Assessment –Streamflows

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In the presentation on Monday 7/13/2020, simulated stream discharge was mistakenly converted to acre-feet per day instead of cubic feet per second. After correcting units, the following changes to the calibration are observed:• Simulated stream discharge values shown in the previous

calibration slide are actually lower by a factor of 2, as shown in the new figure to the right.

• the calibration has improved for all locations and reduced the model error

• we also updated the analysis of streamflow calibration for all 1`1 USGS stream gages in the model area (shown on right)

• These updates are now included in the “Updating the Santa Rosa Plain Hydrologic Model for Use in Development of the Groundwater Sustainability Plain for the Santa Rosa Plain Groundwater Subbasin”

• These updates do not affect the numbers or conclusions for the water budget presented on 7/13/2020. They only impact the calibration assessment.

Surface Water BudgetSubregions and simulated stream reaches


Surface Water BudgetInflows, outflows, and net streambed exchange


Surface Water Budget - SummaryHISTORICAL (WY 1976 TO 2018) SURFACE WATER BUDGET SUMMARY (ACRE-FEET/YEAR)

CURRENT (WY 2012 TO 2018) SURFACE WATER BUDGET SUMMARY (ACRE-FEET/YEAR)


Net Streambed Exchange

Overland Runoff to Streams

Boundary Outflows

Boundary Inflows

Mean 300 130,200 -492,200 362,000 Minimum

-4,400 15,700 -1,161,600 31,200

Maximum 5,200 288,900 -46,600 868,500 Median -100 118,600 -427,600 312,300

Net Streambed Exchange

Overland Runoff to Streams

Boundary Outflows

Boundary Inflows

Mean -1,300 119,900 -432,200 313,700 Minimum -4,400 64,000 -1,077,900 142,600 Maximum 1,100 282,100 -204,500 797,000 Median -600 95,300 -342,900 251,300

Groundwater Budget - Inflows


Groundwater Inflows - SummaryHISTORICAL (WY 1976 TO 2018) GROUNDWATER INFLOWS BUDGET SUMMARY (ACRE-FEET/YEAR)

Deep Percolation of Precipitation and Applied Water

Streambed Recharge to Groundwater

Septic Return Flows

Subsurface Inflow from Surrounding Watershed

Subsurface Inflow from Neighboring Basins

Mean 28,700 15,100 1,000 2,100 7,400 Minimum 2,000 9,100 800 2,000 6,900 Maximum 58,100 19,700 1,200 2,300 8,400 Median 26,500 14,700 1,100 2,100 7,400

CURRENT (WY 2012 TO 2018) GROUNDWATER INFLOWS BUDGET SUMMARY (ACRE-FEET/YEAR) Deep

Percolation of Precipitation and Applied Water

Streambed Recharge to Groundwater

Septic Return Flows

Subsurface Inflow from Surrounding Watershed

Subsurface Inflow from Neighboring Basins

Mean 25,200 14,900 1,200 2,000 7,400 Minimum 12,600 12,300 1,200 2,000 7,100 Maximum 53,400 19,700 1,200 2,100 7,700 Median 20,800 14,700 1,200 2,000 7,400


Groundwater Budget - Outflows


Groundwater Outflows -Summary

Historical (WY 1976 to 2018) Groundwater outflows Budget Summary (acre-feet/year) Agricultural

Pumping Groundwater ET

Subsurface Outflow to Adjacent Basins

Discharge to Streams

Surface Leakage

M&I + Rural Domestic

Mean 9,100 9,400 4,900 15,400 6,200 10,000 Minimum 5,700 7,100 4,500 8,700 2,500 6,500 Maximum 13,900 13,100 5,200 23,400 12,300 13,200 Median 9,000 9,300 4,900 15,400 5,800 10,100


Current (WY 2012 to 2018) Groundwater outflows Budget Summary (acre-feet/year)

Agricultural Pumping

Groundwater ET

Subsurface Outflow to Adjacent Basins

Discharge to Streams

Surface Leakage

M&I + Rural Domestic

Mean 10,400 9,500 4,700 13,700 5,200 9,500 Minimum 8,700 8,600 4,500 10,200 3,200 7,300 Maximum 11,400 11,800 5,000 19,200 9,500 11,200 Median 10,400 9,200 4,700 14,100 5,100 9,900


Historical (WY 1976 to 2018)

Current (WY 2012 to 2018)

Mean -600 -2,100Minimum -22,000 -12,900Maximum 20,000 20,000Median -3,000 -4,500


Historical (WY 1976 to 2018) Groundwater Pumpage

M&I Rural Domestic


Mean 7,900 2,600 9,100Minimum 4,800 2,000 5,700Maximum 11,100 2,900 13,900Median 8,000 2,600 9,000

Current (WY 2012 to 2018) Groundwater Pumpage

M&I Rural Domestic


Mean 7,000 2,900 10,400Minimum 4,800 2,900 8,700Maximum 8,800 2,900 11,400Median 7,300 2,900 10,400

Comparison of Rate Study PumpageEstimates with SRPHM 1.0+Comparing Water Year 2012 pumping from SRPHM 1.0+ with agricultural pumping from Rate Study. Water Year 2012 from SRPHM1.0+ is used because same Land Use dataset used for both studies. Included golf course as TurfGrass from Rate Study in comparison, and removed surface water offset from rate study (235ac ft).

Rate Study did not include Field Crop.

Field Crop Grains Orchard Pasture Truck Crop Turf Grass

Vineyard (Surface

Water Use Not accounted)

Total

Groundwater Pumpage (acre-feet) Water Year 2012 SRPHM 1.0+ 609 243 51 1,975 580 787 5,991 10,236

Rate Study NA 69 123 105 99 595 5,184 6,175

Difference 609 174 (72) 1,870 481 192 807 4,061

Crop Coverage (acres)Water Year 2012 SRPHM 1.0+ 470 360 70 890 510 560 9,240 12,100

Rate Study NA 230 68 NA 55 170 8,640 9,164

Difference 470 129 2 NA 455 390 600 2,936


Comparison of Total Agricultural Pumping Based on Various Applied Water Estimates


◦ Groundwater pumpage from the 3 other sources range from10,256 – 11,358 acre-feet per year, or up to 15,543 depending onhow recycled water is incorporated

◦ Main point: agricultural applied water estimates are highlyuncertain and difficult to estimate

◦ Data Gap

Does not include Turf Grass

Introduction to Watershed Budget(not required by SGMA, but useful to look at for Santa Rosa Plain Subbasin)


Nest Steps –Projected Water Budgets Development

SGMA Requirements

Groundwater conditions 50-years into the future

Incorporate projections of land use change, climate change, and other changes in groundwater demands (such as population increase).

The results of the simulation will be used to assess how the Sustainability Indicators respond to the changing climate and groundwater demands in the future.

If undesirable results are simulated to occur, the GSP will need to plan for projects and management actions that respond to the undesirable results.


Land Use Change and Projected Water Demands - WorkgroupsAGRICULTURAL LAND USE CHANGE

Develop range of projections of agricultural land use change

RURAL DOMESTIC GROWTH PROJECTIONS

Look at areas outside of service areas


The range of projections developed by the workgroups will be presented to the Advisory Committee for further review and selection.

The groundwater flow model will then be updated following the selection of the projections.

Projected Climate Change – Proposed Simulation Approach Choose Projected General Circulation Model (GCM) with specific Greenhouse Gas Emission ScenarioReview DWR recommended GCMs and choose 1 scenario that best represents

projected median conditions in Subbasin and Russian River Watershed area

Update model inputs for: Daily Precipitation Daily Minimum and maximum temperature (converted by model to

evapotranspiration [ET])

Climate data updates provide simulation of: Projected hydrology in the watershed (runoff and streamflow, which relates to

groundwater percolation) Projected irrigation water demands due to changes in projected crop ET



Discussion/Questions?

Sustainable Management Criteria ProposalsObjective: Review and discuss SMC proposals and discuss additional considerations and next steps.

Review Modifications to Subsidence SMC

Water Quality Degradation: Update on input received and next steps


Sustainable Management Criteria UpdateJULY 13, 2020


Land Surface Subsidence: Key Points/Considerations Reminder

• GSAs are only responsible for managing inelastic (or unrecoverable) subsidence caused by groundwater pumping, not responsible for elastic (recoverable) subsidence nor for subsidence caused by anything other than groundwater pumping

• Available datasets do not indicate the occurrence of historical inelastic land surface subsidence due to groundwater pumping within the Subbasin.

• Proposed management of groundwater-levels within or above historical ranges through Chronic Lowering of Groundwater Levels Sustainability Indicator, makes future inelastic subsidence due to groundwater pumping unlikely.


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Summary of Options for Subsidence SMC discussed June 22:evelop range of options for establishing Undesirable Results for Board onsideration with AC input

Dc

1. Definition of Undesirable Result Option #1 • If annual minimum threshold (0.1 ft) exceeded, or any area experiences five continuous years of subsidence even if

each year’s annual subsidence rate is less than the minimum threshold• AND subsidence is determined to be correlated with groundwater level declines due to groundwater pumping.

2. Definition of Undesirable Result Option #2 • If annual minimum threshold exceeded or cumulative subsidence exceeds 0.2 feet total in any area (even if each

year’s annual subsidence rate is less than minimum threshold)• AND subsidence is determined to be correlated with groundwater level declines due to groundwater pumping.

3. Definition of Undesirable Result Option #3 • If annual minimum threshold exceeded or five continuous years of subsidence occurring over 25 contiguous acres

including developed land or infrastructure facilities even if each year’s annual subsidence rate is less than the minimum threshold

• AND subsidence is determined to be correlated with groundwater level declines due to groundwater pumping.

SANTAROSAPLAINGROUNDWATER.ORG

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Results from AC Questionnaire for Subsidence SMC Question AC response

For Option 1 Does the five continuous years of any total subsidence threshold seem too short, too long, or about right?

11 yes (about right), 0 no

For Options 2 & 3

Does the cumulative minimum threshold of more than 0.2 feet seem too low, too high or about right?


For Option 3 Does 25 contiguous acres (equivalent to about 10 pixels of InSAR data) sound too small, too large or about right?


For Option 3 Does adding the condition that the 25 contiguous acres include “developed land or infrastructure” seem appropriate?

1 yes, 7 no

Who is comfortable with Option 1? 6 yes, 2 noWho is comfortable with Option 2? 4 yes, 2 noWho is comfortable with Option 3? 2 yes, 3 no

• Concerns with having proposed annual MT so close to reported measurement accuracy• Interest in combining options• May need additional detail/analysis to support the proposed number of years,

cumulative amount of subsidence and size of contiguous acres.



InSAR Accuracy Information from DWR:

1. The error between InSAR data (>185 million measurement points total) and continuous GPS data (n=137, used as validation points) is 16 mm (0.052 feet) with a 95% confidence level. https://data.cnra.ca.gov/dataset/tre-altamira-insar-subsidence

• This error assessment was for statewide dataset and included calculation of RMSE of 7.9 mm with correlation coefficient of 0.70.

• Local station correlations are better than these statewide estimates

• Santa Rosa Plain station shows RMSE of 2.59 mm and correlation coefficient of 0.83

• May also need to consider any additional error associated with CPGS station data

https://data.cnra.ca.gov/dataset/tre-altamira-insar-subsidence

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InSAR Accuracy Information from DWR

2. The measurement accuracy when converting from the raw InSAR data to the raster map provided byDWR, which was calculated by comparing the point data, is 0.048 feet with 95% confidence level. Addingthis error to that on previous slide yields total error of 0.1 ft.

• We are evaluating whether the annual analysis of InSAR data could be done using the raw point data,rather than DWR’s raster data, which could potentially remove or reduce this error.

• Would also develop procedures for verifying accuracy for any potential future exceedances, which couldinclude:

• Analysis of trends to screen for any potential anomalous data points• Comparison with any available local survey data from Cities, County, etc.



Existing InSARDatasets:

• Existing available datasets for four most recent water years

• No exceedances of proposed annual MT of 0.1 have occurred


Existing InSARDatasets:

• No evidence of “false positives” above error range

• Largest annual changes are less than 0.05 feet

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Applies to All Three Options (current proposal)

• The annual minimum threshold is set to 0.1 feet of subsidence per year (measured at each ~2.5 acre pixel) accounting for inherent InSAR error.

• Any exceedance of a minimum threshold is an undesirable result, if the exceedance is irreversible and caused by groundwater pumping.

• Before establishing that an undesirable result has occurred, evaluate whether the change in ground surface elevation is subsidence due to groundwater pumping or other factors.


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Applies to All Three Options:Subsidence-Groundwater Level Correlation Methodology

Determining if an undesirable result has occurred and requires action:• Review of related land surface elevation data from InSAR and other sources• Review of groundwater elevation measurements and trends in RMP and other nearby wells being

monitored, including an assessment as to whether groundwater levels are below historical lows• Review of seismic related data and records• Evaluation of time series plots of groundwater-levels and land subsidence from nearby monitoring

wells• Evaluation of known or estimated groundwater pumping patterns within the vicinity of any observed

potential subsidence • Compilation of pertinent data and assessment of any data gaps• Determination of whether the cause of subsidence is declining groundwater levels due to

groundwater pumping, if this constitutes an undesirable result, and proposed actions needed to reduce additional potential subsidence in the future.


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Proposed SMC Option for Feedback

Based on the feedback received and the information just provided, staff recommends that:

1. Any rate of future inelastic (irrecoverable) subsidence due to groundwater pumping be considered significant and unreasonable

2. Annual MT be set at 0.1 feet

3. Undesirable result determination also incorporate:

a. A cumulative cap on the total amount of subsidence (initially proposed at 0.2 feet)

Outstanding questions:

1. Should the undesirable result also be triggered if multiple continuous years of subsidence is observed, even if annual is less than 0.1 ft (eg, 5 continuous years)?

2. Should the undesirable result include a minimum-sized area over which subsidence occurs (eg, 25-contiguous acres)?



Water Quality Degradation: Update on input received and next steps

Sustainable Management Criteria: Degraded Water QualityWhat we will cover today:• Reminder of Key Points/Considerations• Incorporating comments received• Preparing for SMC development• Questions and discussion


** This item is to set the stage to craft the SMC for next meeting, and not to weigh in on options.

Degraded Water Quality: Key Points• Degraded groundwater quality is one of the more complex SMCs to develop and several considerations need to be addressed in order to get to the complete SMC development.

• The SMC for this sustainability indicator is considered a “do no harm” metric.

• GSAs should establish a process for routine consultations with other water quality regulatory agencies to discuss ongoing programs and initiatives relevant to the Subbasin, share monitoring data and information, and consider any applicable policy recommendations.

• The GSA must choose from three different metrics to develop minimum thresholds and measurable objectives.

• The GSA needs to identify the list of beneficial users that may be impacted by water quality degradation due to GSP projects and actions.

• The GSA needs to identify the constituents of concern (COCs) that will be monitored during GSP implementation to avoid undesirable results. The COCs are generally tied to the beneficial users listed above.

• The GSA needs to understand the local, state, and federal water quality standards applicable to the selected COCs, before setting the SMC.



Steps for Development of Sustainable Management Criteria for Water Quality

Multiple step process to guide decision making:1. Define level of groundwater quality management and coordination2. Determine type of metric to use 3. Determine and identify beneficial users 4. Define Constituents of Concern (COC) for identified beneficial users5. Determine the limits and concentrations for each COC and category of

beneficial user6. Identify existing water quality monitoring programs that can be used for

setting SMCs7. Establish SMC – Establish Significant and Unreasonable Statement

* Received input from AC members via e-mail

Degraded Water Quality SMC Steps– Recap & Feedback

1. Define level of groundwater quality management and coordination Propose “do no harm” approach – generally agreed by AC members

2. Determine type of metric to use Propose “number of affected supply wells” - general agreement received

3. Determine and identify beneficial users Are drinking water users and agricultural users appropriate? Yes;

comment to add tech industry (industrial users)4. Define Constituents of Concern (COC) for identified beneficial users Proposed As, N, salts; Are there other constituents that should be

considered related to beneficial users? Comments to add boron, chlorides, sodium (for ag), local issues for iron, manganese, selenium, chromium 6 (potentially), PFAS, pharmaceuticals


Degraded Water Quality SMC Steps– Recap & Feedback (cont.)


5. Determine the limits and concentrations for each COC and category of beneficial user For drinking water, recommend using MCLs and SMCLs – agreed For ag users, key criteria are salinity and nitrate – could check Basin Plan

6. Identify existing water quality monitoring programs that can be used for setting SMCs Strongly suggest using the Salt and Nutrient Management Plan Network DDW public supply wells North Coast Water Board’s Dairy Program wells Future project implementation monitoring network wells (e.g. domestic

wells)

Degraded Water Quality SMC Steps– Recap & Feedback (cont.)


7. Establish SMC Review Significant & Unreasonable Statement – any suggested revisions?

– no feedback receivedReview Statement: Significant and unreasonable water quality conditions occur if Santa Rosa

Plain GSP projects or management activities cause an increase in the concentration of constituents of concern in groundwater that lead to adverse impacts on beneficial users or uses of groundwater. Adverse impacts include diminished supply due to water quality impacts, such as non-compliance with drinking water standards or undue costs for mitigating such negative impacts such as wellhead treatment or well replacement.

Next Steps to Develop Minimum Thresholds and Measurable Objectives

• Section §354.28(c)(2) of the Regulations states that “The minimum threshold shall be based on the number of supply wells, a volume of water, or a location of an isocontour that exceeds concentrations of constituents determined by the Agency to be of concern for the basin.”

• In the Santa Rosa Plain Subbasin, minimum thresholds are based on a number of supply wells that exceed concentrations of constituents determined to be of concern for the Subbasin.

• The definition of supply wells for constituents of concern that have an MCL or SMCL are public supply wells. The definition of supply wells for constituents of concern that may lead to reduced crop production are agricultural irrigation supply wells.


Next Steps to Develop Minimum Thresholds and Measurable Objectives (cont.)

•Minimum thresholds are based on a degradation of groundwater quality, not animprovement of groundwater quality. Therefore, this GSP is designed to avoidtaking any action that may inadvertently move groundwater constituents thathave already been identified in the Subbasin in such a way that the constituentshave a significant and unreasonable impact that would not otherwise occur.

•Constituents of concern must meet three proposed criteria:o They must have an established level of concern such as an MCL or SMCL, or a level that

reduces crop productiono They must have been found in the Subbasin at levels above the level of concerno The occurrence of the COC has to be extensive throughout the Subbasino Based on these criteria: staff has identified As, nitrate and salts as COCs moving forward

(additional information is still being gathered)


Questions and DiscussionADDITIONAL AC INPUT WILL ASSIST STAFF IN PREPARING WATERQUALITY SMC FOR REVIEW AT FUTURE AC MEETINGS .


Updates (Time Permitting)Objective: Provide relevant updates that inform the Advisory Committee -AC to ask questions if needed.

Marcus Trotta, Technical Staff◦ Projects and Management Actions ◦ Grants Update◦ Practitioner Workgroups◦ Monitoring Network

Andrea Rodriguez, Outreach Staff◦ Public Outreach Progress Update


Review Meeting Action Items and Discuss upcomingMeeting Agendas


Meeting Adjourns

Upcoming Community Workshop:◦ Wednesday, July 29, 2020, 5:30-7:00pm

Next GSA Board Meeting:◦ Thursday, August 13, 2020, 1:00-3:30pm

Next Advisory Committee meeting:◦ Monday, September 14, 2020, 3:00 – 5:30 pm


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