Impacts of Future Climate Conditions and Forecasted Population Growth on Water Supply Systems in the Puget Sound Region

Abstract

There is evidence that long-term climate change has altered streamflow patterns in the Puget Sound region, particularly during spring and summer months, and forecasts suggests these changes will continue. This research explored the ability of regional water supply systems in the Puget Sound, including the cities of Seattle, Everett, Tacoma, and Bellevue, to meet future demands given such changes. To evaluate regional water supply, three sets of climate impacted streamflows were created for 75-year, daily sequences associated with decades centered on the years 2000, 2025, 2050, and 2075 using three general circulation models and two emission scenarios. The performance of each water supply system, characterized by firm yield and reliability metrics, was determined. Alternative operating procedures were then examined for the systems. This research also evaluated the efficacy of municipal and industrial (M&I) demand curtailments as an emergency mitigation strategy to alleviate future shortfall events. The research determined that climate change will decrease system safe yield in the future and that alternative operating policies or other system changes are necessary to meet projected demands beyond the year 2055.