Margaret Hahn and Dr. Richard Palmer University of Washington Department of Civil and Environmental Engineering Climate Impacts on PNW Municipal Water Supplies
Objective and Outline Assess the impacts of climate change on three neighboring water supply systems Conclusions Background Method Results Response
Conclusions Climate impacts on the four basins’ hydrology are similar Average percent difference in seasonal flows –2020 Winter : 28% 2020 Spring : -20% –2040 Winter : 37% 2040 Spring : -31% Absolute average percent difference –Sultan : 31% –Tolt : 18% –Cedar : 36% –Green : 32% Average supply system impact is 15-17% increase in System Use (surface storage, groundwater and/or system shortfalls)
Background
Evaluation of Climate Change Climate Shift Meteorological Data Hydrology Model Demand Model Operations Model
Precipitation will increase in the winter and decrease in the summer. Temperatures will increase by 2° C by 2040, with higher temperatures in the summer
DHSVM Distributed Hydrology-Soil-Vegetation Model
DHSVM Calibration
Sultan River Inflows into Spada Reservoir Average Annual Hydrograph
Tolt River Inflows into Tolt Reservoir Average Annual Hydrograph
Cedar River Inflows into Chester Morse Reservoir Average Annual Hydrograph
Green River Inflows into Howard Hansen Reservoir Average Annual Hydrograph
Ranked Cumulative Winter Flow (JFM) %43% cfs- weeks
Ranked Cumulative Spring (AMJ) Flow % cfs- weeks
Results – Impacts on Hydrology Percent difference from current climate cumulative seasonal flows JFMAMJJFMAMJ Mean Absolute Percent Difference Sultan Tolt Cedar Green Average
Water Supply System Analysis CRYSTAL Cascade Regional Yield Simulation and Analysis Model Simulation model of Puget Sound water supply Considers future demands, policies, supplies and infrastructures Uses weekly time step Developed in Powersim
Picture of Crystal
Sultan River, Spada Reservoir – Supply Used Max – 37% Min – 0% Avg – 15%
Cedar/Tolt – Supply Used plus Shortfalls Max - 32% Min - 17% Avg - 12%
Green – Supply Used Max - 28% Min - 2% Avg - 16%
Climate Impact on Water Supply Average climate impact on Supply Used, Percent Difference from Current Climate BasinMaxMinAvg Sultan37015 Cedar/Tolt Green28216
Possible Reactions to Climate Change Information Supply –Tacoma to Seattle Connection (2 nd Supply Project) –Seattle to Everett Connection –Water Reuse Demand –Conservation Measures –Pricing –Change Service Base
10,000 acre-ft ~~ 3333 mgal difference in the amount of storage used due to climate change Assume 100 day storage drawdown period Assume 1.3 million customers How much would each person have to conserve? 23 gal per capita during drawdown
Estimated Daily per Capita Water Use, Indoor/Outdoor 95 gpd
Estimated Daily per Capita Water Use, Indoor/Outdoor 72 gpd Overall reduction 25% 72 gpd Reduce outside use 33%10 gpd Upgrade toilets 37%7 gpd Upgrade clothes washer 20%3 gpd Upgrade shower head 23%3 gpd Total23 gpd
Margaret Hahn and Dr. Richard Palmer University of Washington Department of Civil and Environmental Engineering Climate Impacts on PNW Municipal Water Supplies