1. Climate Change Streamflow Scenarios for Pacific Northwest Water Planning Studies
JISAO Center for Science in the Earth System and the
Department of Civil Engineering
University of Washington
October, 2002
Alan F. Hamlet
Amy Snover
Dennis P. Lettenmaier

2. Climate Change Scenarios
Long term planning for climate change may include a stronger emphasis on drought contingency planning, testing of preferred planning alternatives for robustness under various climate change scenarios, and increased flexibility and adaptation to climate and streamflow uncertainty.
Observed Streamflows
Planning Study
Altered Streamflows
Climate Change Scenarios
Other Inputs

3. Changes in Mean Temperature and Precipitation or Bias Corrected Output from GCMs
ColSim
Reservoir
Model
VIC
Hydrology Model

4. Climate Change Scenarios 2040s

5. The main impact: less snow
April 1
Columbia
Basin
Snow
Extent

6. Columbia River at The Dalles 2040s “Middle-of-the-Road” Scenario

7. Water Management Agencies
The Problem: Different Tools Different Objectives
Water Management Agencies
Academic Research
Climate Research
Hydrologic Studies
Integrated Assessment
Adaptation Strategies
Formal Planning Exercises
Monitoring
Infrastructure
Water Management

8. Project Goals:
Create climate change streamflow scenarios that cover the same period of record and are numerically consistent with the historic record of streamflows traditionally used in water planning studies.
Make these streamflow scenarios freely available on the web for a large number of river locations to facilitate the incorporation of climate change information into existing water planning efforts in the PNW.

9. Bias Correction Objectives:
Raw
Bias Corrected
Result: Bias corrected hydrologic simulations are quite consistent with observed streamflows in absolute value and climate change signals are translated without significant distortion.

10. Final Adjustment to Observed Data
For an overlapping simulated and observed time series, apply monthly changes in bias corrected hydrologic simulations to observed streamflow record.
Final Product

11. Overview of Preliminary Web-Based Data Archive

15. Planned Project Extensions
Winter :
Extend the number of sites to support specific planning and research activities at the UW, Northwest Power Planning Council, and Idaho Department of Water Resources.
Longer Term:
Extend the period of record of the data to
Extend the number of climate change scenarios.

16. Conclusions
Water policy workshops (Skamania 2001) have highlighted the need to inject climate change information into existing river basin planning activities where possible and to provide access to free streamflow scenarios to help reduce costs.
Water planning activities at many water management agencies tend to be strongly linked to internally developed planning tools driven by a particular period of observed streamflows.
Our project produces “adjusted” realizations of the historic streamflow record based on simulations from a physically based hydrologic model driven by simple climate change scenarios.
Such climate change “forecasts” can be used in a straight forward manner in water planning studies that currently use the observed record of streamflows for planning.