# Presentation: 153405

## Decision Relevant Climate Change Impact Assessments using WEAP21

- Stockholm Environment Institute-Boston Center
- National Center for Atmospheric Research
- Natural Heritage Institute
- with support from:
- U.S. EPA, Office of Research and Development

## Let’s start with a quick introduction to the original version of WEAP, and most other water resource management simulation models for the matter.

## A Simple System

## What are we assuming?

- That we know how much water is flowing at the top of each river.
- That we know how much water is flowing into or out of the river as it moves downstream.
- That we know what the water demands are with certainty.

## What are we assuming?

- That we know how much water is flowing at the top of each river.
- That we know how much water is flowing into or out of the river as it moves downstream.
- That we know what the water demands are with certainty.
- 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?

## 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?

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

## WEAP Hydrology

## The WEAP 2-Bucket Hydrology Module

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

## One 2-Bucket Model Per Land Class

## This last point leads to a stylized groundwater representation

## An Example from California

## WEAP Schematic of Sacramento Watershed Based Model

## Calibration and Validation

**Model Evaluation (1961-1999):**
- Flows Along Mainstem and Tributaries
- Reservoir Storage and Release
- Trinity Diversion
- Agricultural Water Demand
- Groundwater Storage Trends
- Yolo Bypass Flood Inundation
- Sacramento River Water Temperature

**Notes:**
Process of establishing credibility, legitimacy, and, relevancy 

## Reservoir Storage

- SHASTA

## Stylized Sacramento Climate Scenarios

**Stylized Sacramento Climate Scenarios**

## Phenologies of reproductive events in freshwater phase of Chinook salmon life-cycle in the SV watershed.□ = adult immigration; ∆ = spawning and hatching; ◊ = juvenile emigration

## River Temperature Model

- First-order DO and temperature patterned after Chapra (1997)
- Water quality simulated for select rivers, where tributaries, discharges, and return flows prescribed.
- Mass balance equations for each stream segment
- Hydrologic inflows from rivers and groundwater sources simulate the water balance and mixing of concentrations and temperature along each reach.
- Same River network for the water resources and the water quality simulation, and assumes complete mixing.

## Temp. Profile – Kms Downriver of Shasta Dam

|  | June | July | Aug | Sep |
| --- | --- | --- | --- | --- |
| Historic | 100 | 55 | 65 | 220 |
| WmDry | 55 | 14.5* | 14.9* | 50 |
| WmWet | 65 | 40 | 35 | 110 |

## Current Decision-Relevant Activity

- Collaborating with PCWA and EID on the development of a WEAP21 model of the American River Watershed for exploration of potential climate change impacts.
- Collaborating with DWR to see if the WEAP21 Framework can contribute to the “quantitative climate change assessment” envisioned for B160-2010.
- Working with the California Climate Center on a case study for the Sacramento Valley as part of a climate change assessment report called for under Governor Schwarzenegger’s Executive Order S-3-05.

## Approach

- Develop refined WEAP model of the American River watershed.
- Apply the model to understand hydropower potential of PCWA system.
- Apply the model to understand the drought vulnerability of the EID water supply system.
- Potentially integrated with a model of the Yuba River watershed which is managed by Nevada Irrigation District and has substantial transfers into the American River watershed.

## The American River Watershed in WEAP21

## North Fork American

## Preliminary Calibration 1990 - 1999

## Warmer and Drier  Climate Scenario

## Current Decision-Relevant Activity

- Collaborating with PCWA and EID on the development of a WEAP21 model of the American River Watershed for exploration of potential climate change impacts.
- Collaborating with DWR to see if the WEAP21 Framework can contribute to the “quantitative climate change assessment” envisioned for B160-2010.
- Working with the California Climate Center on a case study for the Sacramento Valley as part of a climate change assessment report called for under Governor Schwarzenegger’s Executive Order S-3-05.

## Approach

- Train DWR staff on the use of WEAP.
- Develop a link between Sacramento Valley application and a Delta Water Quality Model.
- Develop a link with a future demand scenario generator developed by RAND.
- Embed the Sacramento Valley application in a more stylized system-wide model.
- Run a series of climate change scenarios.
- Evaluate with DWR if the WEAP framework can be used for quantitative climate change analysis in Bulletin 160-2010.

## Current Decision-Relevant Activity

- Collaborating with PCWA and EID on the development of a WEAP21 model of the American River Watershed for exploration of potential climate change impacts.
- Collaborating with DWR to see if the WEAP21 Framework can contribute to the “quantitative climate change assessment” envisioned for B160-2010.
- Working with the California Climate Center on a case study for the Sacramento Valley as part of a climate change assessment report called for under Governor Schwarzenegger’s Executive Order S-3-05.

## Approach

- Disaggregate HUCs to ID level
- Calibrate model
- Run climate change scenarios
- Modify assumptions (e.g. changing irrigation technology/efficiency, varying cropping patterns, conversion of farmland to urban use, etc.)
- Re-run scenarios
- Perform economic assessment

## Spatial Disaggregation

- Sacramento Valley
- WEAP Model

## Spatial Disaggregation

- Stone Corral HUC

- Before

- After

## Model Calibrated for Stone Corral

- Regional water consumption and delivery within Sacramento-Stone Corral HUC corresponds to historic data.
- Irrigation district level water consumption and delivery reflects historic observations.
- Groundwater levels follow historic trend.

## Future Work

- Disaggregate and calibrate Lower Butte HUC
- Run climate change scenarios
- Modify Assumptions (e.g. add dynamic cropping patterns)
- Perform economic assessment

## 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, with the real potential to influence decision-making processes.