Seminar Abstract

Richard Palmer and Matthew Wiley

Thursday, May 6, 2004
1:30 to 3:00

Evaluating the Impacts of Climate Change on Municipal Water Supplies:
Preliminary Results from a Recent Study

The preponderance of evidence in the scientific community supports the theory that global climate is changing. The effect of climate change on natural and man-made systems remains less certain. Municipal water supplies, particularly those that rely on summer snowmelt to augment storage capacity, are at risk of significant changes from the historic streamflow regime to which they have become accustomed. There are few standardized methods established for assessing the impacts of climate change to municipal water supplies. Frederick and Gleick (1999) propose evaluating climate change impacts on water resources using a three stage modeling approach: General Circulation Models (GCMs) to simulate global climate, basin scale hydrology models, and water resource system simulation models.

This talk investigates the application of the Frederick and Gleick method to the water supply system for the city of Seattle, Washington and the uncertainty that is associated with each stage of the process. Specific attention is given to the techniques necessary for downscaling climate data from the global scale to the basin scale. Among the modeling stages, the greatest source of uncertainty arises from the wide range of future scenarios produced by GCMs. The magnitude of this uncertainty presents challenges in quantifying the exact impacts of climate change on the water supply. Solutions to these challenges are explored in the presentation. Among the recommendations is that multiple climate models be used, generating an ensemble average that quantifies the most likely impact.