Precipitation Patterns, Supply Planning and Demand Curves: Assessing Water Supply Risks in a Changing Climate Erica Brown Association of Metropolitan Water Agencies (AMWA) May 21, 2015 NOAA CPO Third Thursday Webinar Series Climate Information for Managing Risks in Water Resources

Overview Water supply planning: what the demand curves show buys utilities time, re: for supply development Water supply planning: what the demand curves show buys utilities time, re: for supply development Two illustrative examples from: Two illustrative examples from: Seattle/Cascade Water Alliance and extreme events Seattle/Cascade Water Alliance and extreme events Tarrant Regional Water District and prolonged drought Tarrant Regional Water District and prolonged drought Near-term (and long term) informational and forecast needs and improvements Near-term (and long term) informational and forecast needs and improvements Regional-long term resilience planning Regional-long term resilience planning

Case examples for today’s talk Seattle Public Utilities/Cascade Water Puget Sound region, Pacific NW Puget Sound region, Pacific NW Seattle supplies finished water to Cascade Water and its population Seattle supplies finished water to Cascade Water and its population Pop. Served 1.45 M Pop. Served 1.45 M Short on storage, long on precip. Short on storage, long on precip. Tarrant Regional Water District North Central Texas Supplier of raw water to 30 wholesale customers in 11 counties Pop. served 1.7 M Long on storage, short on precip.

These two agencies, like most around the U.S., have declining demand despite population growth. Nationally, water use in the U.S. for public supply declined by 5% between 2005 and 2010 (USGS, 2014) Water Consumption Is Declining

Shifting Water Demand Forecasts (Seattle Public Utilities, Including Cascade) 5

Factors causing changes in demand trends Plumbing efficiency and regulation Plumbing efficiency and regulation Housing stock and density Housing stock and density Conservation behavior and technology Conservation behavior and technology Water system efficiency Water system efficiency Kind of water use Kind of water use Irrigation Irrigation Residential Residential Business Business Population demographics Population demographics Water use policy and pricing Water use policy and pricing

Lower demand buys time for supply development

Short on storage – long on water Snow=savings plan Snow=savings plan Rain=checking account Rain=checking account Near term: managing operationally with the best data and information they have. Near term: managing operationally with the best data and information they have. What does snowpack will decline mean? Seattle Area climate issue: amount and timing of precipitation/runoff As long as you’re not in the red, you don’t need a savings account. Keep making deposits into checking and you’re good. – Chuck Clarke, Cascade Water Alliance CEO Source: SPU

Management of reservoirs based on detailed watershed simulation model Management of reservoirs based on detailed watershed simulation model

Source: SPU

TRWD climate issue: drought TRWD climate issue: drought Long on storage, short on water. Drought Risks: Transmission capacity Transmission capacity Reliability Reliability Source supply availability Source supply availability The 20-mile Eagle Mountain Connection allows TRWD to extend the reach of water from its E. TX reservoirs to Eagle Mountain Lake via storage and transmission facilities. Source: Freese.com

Palmer Index History - extreme drought FSource: TRWD

TRWD Demands Over Time

Forecasts and information helpful for extreme event planning Continued refinement and improvements are always welcome! Continued refinement and improvements are always welcome! Improvements in 1-3 day forecasts (reliability, specificity) - Seattle Improvements in 1-3 day forecasts (reliability, specificity) - Seattle Improvements in confidence levels for 7-14 day forecasts - Seattle and Tarrant Improvements in confidence levels for 7-14 day forecasts - Seattle and Tarrant Improvements in seasonal outlooks for precipitation - Seattle Improvements in seasonal outlooks for precipitation - Seattle Improved bounding of uncertainties in forecasts that do exist (e.g., Dec Pineapple Express event; ensembles of QPF forecasts) –- Seattle and Tarrant Improved bounding of uncertainties in forecasts that do exist (e.g., Dec Pineapple Express event; ensembles of QPF forecasts) –- Seattle and Tarrant

Water Resilience in the Future

Tarrant Regional water planning (legislated) Regional water planning (legislated) 5 year plan – but looking at 50 years out for population and demand 5 year plan – but looking at 50 years out for population and demandSeattle/Cascade Regional water planning (voluntary) Regional water planning (voluntary) Long term outlooks (20-year) continually updated with new (population and climate) scenarios, inputs Long term outlooks (20-year) continually updated with new (population and climate) scenarios, inputs

Thank you Erica Brown AMWA Thanks to:  Laura Blaylock, Tarrant Regional Water District  Julie Hunt, Trinity River Authority of Texas  Chuck Clarke, Cascade Water Alliance  Alan Chinn, Paul Fleming, Seattle Public Utilities

Extra slides

Cascade Water Alliance Service Area

Cascade Average Daily Demand (million gallons per day) 27

Example: Seattle Source: SPU

Seattle: precipitation on track Source: SPU

Seattle: reservoir storage on track Source: SPU