2013 UPDATE Spokane Valley-Rathdrum Prairie Aquifer Water Demand Forecast Update Rob Lindsay Water Resources Manager Spokane County Utilities Spokane River Forum Conference March 27, 2013

Spokane Valley-Rathdrum Prairie Aquifer Water Demand Forecasts Presented by: Mike Hermanson Water Resources Specialist Spokane County Utilities Spokane River Forum Conference May 23, 2011

Presentation Overview Review Spokane County Water Demand Model (2010) and 2012 Updates Idaho Future Demand Study Summary

History 2010 –Idaho Future Demand Study Draft Results presentation –Spokane County Water Demand Model presentation of project goals, objectives, concepts –Spokane County presented results of Water Demand Model, compared two studies 2013 –Spokane County performed updates to the Water Demand Model

Background Project funded by Washington Dept. of Ecology A county-wide, multi-WRIA project Performed by CDM, supported by local advisory committee

Background Evaluations based on: –Use Sectors (public supply, agricultural, industrial, self supply) –Geographic Location (SRTC, TAZ) –Population (current census, STRC forecasts) –Variable Weather –Variable Conservation Scenarios –Time

Spokane County Water Demand Model Segregated by Water Use Sector –each subsector has a unique submodel, or way of calculating water demand

Spokane County Water Demand Model Total daily water use per single family residence Indoor water use Outdoor water use Indoor consumptive use Indoor non- consumptive use Onsite septic Sanitary sewer Water use per ft 2 of irrigated landscape Outdoor consumptive use Outdoor non- consumptive use % Consumptivearea of irrigated landscape ET Rate Return Flow UPDATE - Residential Consumptive/Non Consumptive Segregation

Spokane County Water Demand Model 2010 –2000 census –2008 SRTC forecast –487 separate forecast units ( aka TAZ; transportation analysis zone) 2012 –2010 census –2010 SRTC forecast –+/- 500 TAZs A unique water demand calculation is done for each forecast unit

Demand from SVRP Aquifer from Spokane County Spokane County Water Demand Model

SectorModeledReportedRPD Total Production41,89541, % Single Family Residential15,92015, % Multi Family Residential3,9964, % Total Residential19,91619, % Commercial/Industrial9,5289, % Total Non Residential10,75810, % Non Revenue3,4333, % Annual Public Water System Use: Modeled vs. Reported Reported in millions of gallons per year Spokane County Water Demand Model

Monthly Demand from SVRP Aquifer from Spokane County 156 CFS difference Spokane County Water Demand Model

Year2008 SRTC Forecast2010 SRTC Forecast ,661157, ,812174, ,472195, ,132207,270 UPDATE - Comparison of 2008 & 2010 SRTC Forecast of Single Family Dwelling Units

Conservation and Weather –Conservation efforts can be masked by changes in weather Spokane County Water Demand Model no conservation

Idaho Future Demand Study Includes an estimate of current and future use by water use sector on an annual basis: –Public Water Systems –Self Supplied Domestic –Self Supplied Commercial & Industrial –Agriculture Separates Irrigation and Non-Irrigation Use

Evaluates consumptive vs. non consumptive use Range of population & employment growth scenarios Detailed analysis of conservation scenarios Evaluation of potential climate change impacts Idaho Future Demand Study

Aquifer Total Demand to 2040 –Washington +/- 33 %; Idaho +/- 40% WA & ID Demand Idaho scenario – medium growth & no conservation

Updated Model Applications Model Applications –Support local agencies in regional planning/forecasts –Recent updates now support analyses to asses impacts of inter-basin water transfers, including SVRP to Latah Creek, west plains and the Little Spokane River –Updates will support and inform the proposed hydrogeologic model development in the Little Spokane River basin –Evaluates scenarios to assess potential impacts from climate change

Spokane County Water Demand Model Thank You Questions?

Impact of weather on water use Spokane County Water Demand Model