Decision Tools to Evaluate Vulnerabilities and Adaptation Strategies to Climate Change

The Water Resource Sector

Outline

Vulnerability and adaptation with respect to water resources

Hydrologic implications of climate change for water resources

Topics covered in a water resources assessment Viewing water resources from a services

perspective Tools/models WEAP model presentation

Effective V&A Assessments

Defining V&A assessment Often V&A is analysis, not assessment Why? Because the focus is on biophysical

impacts, e.g., hydrologic response, crop yields, forests, etc.

However, assessment is an integrating process requiring the interface of physical and social science and public policy

Effective V&A Assessments (continued)

General questions What is the assessment trying to influence? How can the science/policy interface be

most effective? How can the participants be most effective in

the process? General problems

Participants bring differing objectives/ expertise

These differences often lead to dissention/ differing opinions

Effective V&A Assessments (continued)

To be valuable, the assessment process requires Relevancy Credibility Legitimacy Consistent participation

An interdisciplinary process The assessment process often requires a tool The tool is usually a model or suite of models These models serve as the interface This interface is a bridge for dialogue between

scientists and policy makers

Water Resources – A Critical V&A Sector

Often critical to both managed and natural systems

Human activity influences both systems

Natural Systems

External Pressure

State of System

Little Control of processes

ManagedSystemsExternal

Pressure Product, good or service

Process Control

Example: Agriculture Example: Wetlands

services

Examples of Adaptation – Water Supply

Construction/modification of physical infrastructure Canal linings Closed conduits instead of open channels Integrating separate reservoirs into a single system Reservoirs/mydroplants/delivery systems Raising dam wall height Increasing canal size Removing sediment from reservoirs for more storage Interbasin water transfers

Examples of Adaptation – Water Supply (continued)

Adaptive management of existing water supply systems

Change operating rules Use conjunctive surface/groundwater supply Physically integrate reservoir operation

system Coordinate supply/demand

Examples of Adaptation – Water Supply (continued)

Policy, conservation, efficiency, and technology Domestic

Municipal and in-home re-use Leak repair Rainwater collection for nonpotable uses Low flow appliances Dual supply systems (potable and nonpotable)

Agricultural Irrigation timing and efficiency Lining of canals, closed conduits Drainage re-use, use of wastewater effluent High value/low water use crops Drip, micro-spray, low-energy, precision application

irrigation systems Salt-tolerant crops that can use drain

water

Examples of Adaptation – Water Supply (continued)

Policy, conservation, efficiency, and technology (continued)

Industrial Water re-use and recycling Closed cycle and/or air cooling More efficient hydropower turbines Cooling ponds, wet towers and dry towers

Energy (hydropower) Reservoir re-operation Cogeneration (beneficial use of waste heat) Additional reservoirs and hydropower stations Low head run of the river hydropower Market/price-driven transfers to other activities Using water price to shift water use between sectors

Tools in Water Resource V&A Studies

Hydrologic models (physical processes) Simulate river basin hydrologic processes Examples – water balance, rainfall-runoff, lake

simulation, stream water quality models Water resource models (physical and

management) Simulate current and future supply/demand of

system Operating rules and policies Environmental impacts Hydroelectric production Decision support systems (DSS)

for policy interaction

Tools in Water Resource V&A Studies (continued)

Economic models Macroeconomic

Multiple sectors of the economy General equilibrium – all markets are in

equilibrium Sectoral level

Single market or closely related markets (e.g., agriculture)

Firm level Farm-level model (linear programming

approach) Microsimulation

Hydrologic Implications of Climate Change

Precipitation amount Global average increase Marked regional differences

Precipitation frequency and intensity Less frequent, more intense (Trenberth et al., 2003)

Evaporation and transpiration Increase total evaporation Regional complexities due to plant/atmosphere

interactions

Hydrologic Implications of Climate Change (continued)

Changes in runoff Despite global precipitation increases,

areas of substantial runoff decrease Coastal zones

Saltwater intrusion into coastal aquifers Severe storm-surge flooding

Water quality Lower flows could lead to higher contaminant

concentrations Higher flows could lead to greater leaching and

sediment transport

Africa Example – ECHAM4/OPYC

Africa Example – GFDLR30

What Problems Are We Trying to Address?

Water planning (daily, weekly, monthly, annual) Local and regional Municipal and industrial Ecosystems Reservoir storage Competing demand

Operation of infrastructure and hydraulics (daily and sub-daily)

Dam and reservoir operation Canal control Hydropower optimization Flood and floodplain inundation

Water quantityWater quality

Seasonality of flowRegulation

Water for agriculture

Domestic water

Water for industry

Water for nature

Water for recreation

The Water Resource SectorWater’s “Trade-Off” Landscape

Water Resources from a Services Perspective

Not just an evaluation of rainfall-runoff or streamflow

But an evaluation of the potential impacts of global warming on the goods and services provided by freshwater systems

Extractable; Direct Use; Indirect Use

Recre-

ation, aesth. beauty

Trans-port

Power gener.

Nutr. cycl-ing

Regen. of soil fertility

Water for ag., urban, indust.

Har-vest. biota

Flood/

drought

mitig.

Water purifi-

cation

Ero-sion

con-trol

Habitat/

biodi-versity

Bay

Delta

Lower Rivers

Upper Rivers

Recre-

ation, aesth. beauty

Trans-port

Power gener.

Nutr. cycl-ing

Regen. of soil fertility

Water for ag., urban, indust.

Har-vest. biota

Flood/

drought

mitig.

Water purifi-

cation

Ero-sion

con-trol

Habitat/

biodi-versity

Bay

Delta

Lower Rivers

Upper Rivers

Freshwater Ecosystem Services

Tools to Use for the Assessment: Referenced Water Models

Planning WEAP21 (also

hydrology) Aquarius SWAT IRAS (Interactive

River and Aquifer Simulation)

RIBASIM MIKE 21 and

BASIN

Referenced Water Models (continued)

Operational and hydraulic HEC

HEC-HMS – event-based rainfall-runoff (provides input to HEC-RAS for doing 1-d flood inundation “mapping”)

HEC-RAS – one-dimensional steady and unsteady flow

HEC-ResSim – reservoir operation modeling

WaterWare RiverWare MIKE11Delft3d

Current Focus – Planning and Hydrologic Implications of Climate Change

Select models of interest Deployed on PC; extensive documentation;

ease of use WEAP21 SWAT HEC suite Aquarius

Physical Hydrology and Water Management Models

AQUARIS advantage: Economic efficiency criterion requiring the reallocation of stream flows until the net marginal return in all water uses is equal

Cannot be climatically driven

Physical Hydrology and Water Management Models (continued)

SWAT management decisions on water, sediment, nutrient and pesticide yields with reasonable accuracy on ungauged river basins. Complex water quality constituents.

Rainfall-runoff, river routing on a daily timestep

Physical Hydrology and Water Management Models (continued)

WEAP21 advantage: seamlessly integrating watershed hydrologic processes with water resources management

Can be climatically driven

Physical Hydraulic Water Management Model

HEC-HMS watershed scale, event based hydrologic simulation, of rainfall-runoff processes

Sub-daily rainfall-runoff processes of small catchments

Overview WEAP21

Hydrology and planningPlanning (water distribution) examples and exercisesAdding hydrology to the modelUser interfaceScaleData requirements and resourcesCalibration and validationResultsScenariosLicensing and registration

You can create multiple scenarios and use this box to switch between them.

Use the View bar to switch between your analysis and its results.

Data are organized in a tree structure that you edit by right-clicking here.

Your data are shown here as either a graph or a table.

Enter or edit your data by typing it here.

Hydrology Model

Critical questions How does rainfall on a catchment translate into flow

in a river? What pathways does water follow as it moves

through a catchment? How does movement along these pathways impact

the magnitude, timing, duration, and frequency of river flows?

Planning Model Critical questions

How should water be allocated to various uses in time of shortage?

How can these operations be constrained to protect the services provided by the river?

How should infrastructure in the system (e.g., dams, diversion works) be operated to achieve maximum benefit?

How will allocation, operations, and operating constraints change if new management strategies are introduced into the system?

A Simple System with WEAP21

60

40

An Infrastructure Constraint

70

3010 Unmet

A Regulatory Constraint

70

3010 Unmet

IFR Met

0

40

60

10 unmet

Different Priorities

For example, the demands of large farmers (70 units) might be Priority 1 in one scenario whereas the demands of smallholders (40 units) may be Priority 1 in another

30

10

90

0

Different Preferences

For example, a center pivot operator may prefer to take water from a tributary because of lower pumping costs

Example

How much water will the site with 70 units of demand receive?

Example (continued)

How much water will be flowing in the reach between the Priority 2 diversion and the Priority 1 return flow?

Example (continued)

What could we do to ensure that this reach does not go dry?

What Are We Assuming?

• That we know how much water is flowing at the top of each river

• That no water is naturally flowing into or out of the river as it moves downstream

• That we know what the water demands are with certainty

• Basically, that this system has been removed from its hydologic context

What Do We Do Now?

Add Hydrology

And this is the Climate Interface

Integrated Hydrology/Water Management Analytical Framework in

WEAP21

City

Irrigation

The WEAP 2-Bucket Hydrology Module

Smax

Rd z1

Interflow = f(z1,ks, 1-f)

Percolation = f(z1,ks,f)

Baseflow = f(z2,drainage_rate)

Et= f(z1,kc, , PET)

Pe = f(P, Snow Accum, Melt rate)

Plant Canopy

P

z2

L

u

Surface Runoff =f(Pe,z1,1/LAI)

Sw

Dw

One 2-Bucket Model per Land Class

Some Comments

The number of parameters in the model is fairly limited and is at least related to the biophysical characteristics of the catchment

The irrigation routine includes an implicit notion of field level irrigation efficiency

Seepage can only pass from the lower bucket to the river, not the other way

This Last Point Leads to a Stylized Groundwater Representation

hd

lw Sy,Ks

Percolation

Pumping

Some Comments

The geometry of the aquifers in question is representative, not absolute

The stream stage is assumed to be invariant in this module

Although the “water table” can fluctuate, it ignores all local fluctuations

You can click and drag elements of the water system from the legend onto the schematic directly.

Use the menu to do standard functions such as creating new areas and saving.

Your can zoom your schematic in or out by sliding the bar here.

GIS layers can be added here.

Use the View bar to switch between your data and its results.

The WEAP21 Graphical User Interface

Languages:

Interface Only

English

French

Chinese

Spanish

You can create multiple scenarios and use this box to switch between them.

Use the View bar to switch between your analysis and its results.

Data are organized in a tree structure that you edit by right-clicking here.

Your data are shown here as either a graph or a table.

Enter or edit your data by typing it here.

WEAP’s Temporal and Spatial Scale

Time step: daily, weekly, monthly, etc. No routing, because all demands satisfied

within the current time step Time step at least as long as the residence

time of period of lowest flow Larger watersheds require longer time steps

(e.g., one month) Smaller watersheds can apply shorter time

steps (e.g., 1-day, 5-day, 10-day)

Some Ideas onCatchment Size

Small: < 100 km2

Medium: 100 to 1,000 km2

Large: 1,000 to 10,000 km2

Very large: 10,000 to 100,000 km2

Data Requirements

Prescribed supply (riverflow given as fixed time series) Time series data of riverflows (headflows) cfs River network (connectivity)

Alternative supply via physical hydrology (watersheds generate riverflow) Watershed attributes

Area, land cover . . . Climate

Precipitation, temperature, windspeed, and relative humidity

Data Requirements (continued)

Water demand data Municipal and industrial demand

Aggregated by sector (manufacturing, tourism, etc.)

Disaggregated by population (e.g., use/capita, use/socioeconomic group)

Agricultural demands Aggregated by area (# hectares, annual water-

use/hectare) Disaggregated by crop water requirements

Ecosystem demands (in-stream flow requirements)

Example Data Resources

Climate http://www.mara.org.za/climatecd/info.htm Hydrology http://www.dwaf.gov.za/hydrology/ GIS http://www.sahims.net/gis/ General http://www.weap21.org (resources)

Calibration and Validation

Model evaluation criteria Flows along mainstem and tributaries Reservoir storage and release Water diversions from other basins Agricultural water demand and delivery Municipal and industrial water demands and

deliveries Groundwater storage trends and levels

Modeling Streamflow

Reservoir Storage

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S H A S T A

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Change units and sub-categories of results, and change the style of the graph here.

Select values for the y-axis here.

Select results to be viewed, including which scenario here.

Looking at Results

WEAP21 – Developing Climate Change and Other Scenarios

The scenario editor readily accommodates scenario analysis, e.g., Climate change scenarios and assumptions Future demand assumptions Future watershed development assumptions

Licensing WEAP

Go to www.weap21.org and register for a new license (free for government, university, and non-profit organizations in developing countries)

Register WEAP under Help menu and select “Register WEAP”