The Water Evaluation and Planning (WEAP) System: A Decision Support Tool for Water Management Adaptation to Climate Change

David PurkeyDirector, Water Resources Modeling and Analysis Unit

Natural Heritage InstituteSacramento, California

National Center for Environmental Assessment

Office of Research and Development

U.S. Environmental Protection Agency

EPA Global Change Research Program

Financed 3 research teams to attempt to develop a climate change impact and adaptation framework for water resources and aquatic ecosystems.

Our research team, comprised of:•Stockholm Environment Institute•National Center for Atmospheric Research•Natural Heritage Institute

used the Water Evaluation and Planning (WEAP)system as a starting point for a pilot application in California’s Sacramento Valley.

Let’s start with a quick introduction to the original version of WEAP, and most other water resource planning

models for the matter.

A Simple Planning Model

Planning Model

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

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

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

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

What are we assuming?1. That we know how much water is flowing at

the top of each river.2. That we know how much water is flowing

into or out of the river as it moves downstream.

3. That we know what the water demands are with certainty.

4. Basicly, that this system has been removed from it HYDROLOGIC context.

What do we do now?

ADD HYDROLOGY!

Hydrology Model

Critical question: How does rainfall on a catchment translate into flow in a river?

Critical question: What pathways does water follow as it moves through a catchment? Runoff? Infiltration? ET? Seepage?

Critical question: How does movement along these pathways impact the magnitude, timing, duration and frequency of river flows?

WEAP, with its integrated Hydrology Molude, provides a framework for answering both set of questions.

Application of WEAP to the American River Basin

Input Data Requirements

• Catchment delineation and characterization• Climate data• Infrastructure operations

Model Catchments

Modeled Rivers

Modeled Reservoirs

Modeled Transfers

Calibration Results

North Fork American at North Fork Dam

0

5000

10000

15000

20000

25000

30000

35000

40000

O N D J F M A M J J A SDate

Acr

e-Fe

etSimulated Observed

Caples Lake SWE

0

10

20

30

40

50

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70

Dec-88 Dec-89 Dec-90 Dec-91 Dec-92 Dec-93 Dec-94 Dec-95 Dec-96 Dec-97 Dec-98 Dec-99 Dec-00

Date

Inch

es

Observed Simulated

A Climate Change Scenario

Sample Climate Scenario

• Temperature increase of 1 degree Celsius by 2020.

• Decrease in precipitation of 5% by 2020.

2016-2020

1996-2000Upper South ForkSilver Creek SWE

2016-2020

1996-2000Ice House Reservoir Inflow

2016-2020

1996-2000Ice House Storage

2016-2020

1996-2000

Ice House Generation

Adaptation – Alter Ice House Guide Curve

0

10

20

30

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40 44 48 52 4 8 12 16 20 24 28 32 36

Week

TAF

AdjustedOriginal

Adj. Guide Curve

Current Guide Curve

Ice House Storage

Adj. Guide Curve

Current Guide Curve

Ice House Generation

Conclusions

• The hydrology module is a powerful tool for considering changing catchment dynamics.

• Hydrology is essential for conducting rigorous analysis of climate change impacts.

• Hydrology could be very interesting for sectoral economic analysis because it considers several resources in a catchment, rainfed and irrigated agriculture, forest and range management, fish appropriate flows.

• Increasing activity is taking place with the WEAP21 Framework in California.