Last updated November 16, 2019

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206 Glover Street / PO Box 1212    Twisp, WA  98856

Water Accounting Project

How will water availability affect future development in the Methow Valley?  The Water Accounting Project is helping us find out. 

The Methow Watershed Council (MWC) is charged with managing our water supply according to the Methow Valley’s Instream Flow Rule (“the Rule”), which sets legal limits on water withdrawal.  The Water Accounting Project is evaluating current and future water use to support the community in creating a vision for the Methow’s future. 

The Rule applies to most single-family domestic use in unincorporated areas in the Methow Watershed.  It limits water withdrawn for those uses to 2 cubic feet per second (cfs) from each of seven river reaches in the Methow basin (“the Reservation”).  Once those limits have been reached, further development would require another source of water.  The seven reaches are: Methow Headwaters, Early Winters, Upper Methow, Chewuch River, Middle Methow, Twisp River, and Lower Methow. 

How are we evaluating water use?

In 2011, the MWC developed the Instream Flow Reservation (IFR) Database to estimate the effects of development on water use and availability in the Methow Basin.  The database was updated in 2019 to account for changes in zoning and new and revised data.  It provides an estimate of water availability based on current zoning and projected build-out. 

The estimates in the IFR Database are based on the MWC’s current water-use estimate of 710 gallons per house per day for indoor, limited irrigation, and stock water use.  Using that estimate, 2 cfs is enough water for about 1,820 houses.

Refining the water-use estimate

The MWC ‘s water-use estimate—710 gallons per house per day—is based on several sources of data, including climatic data, meter data, water use rates for crops and livestock, and agricultural census data; estimates developed by the Methow Basin Planning Unit; and aerial photo analysis.  The estimate is also based on use during July—the month during which the largest quantity of water is likely to be used. 

The MWC wants to refine the estimate to better understand how much water local households actually use.  The Council will begin recruiting landowners for a voluntary metering pilot program in Spring 2019.  (Click here if you are interested in participating.)  The MWC hopes to work with a small number of landowners to gather preliminary data.  Meters will be installed at no charge and read remotely. 

Click here for a flier about the Metering Program.

Then what?

Data from the voluntary metering pilot program will guide the MWC in creating a work plan.  We expect to use the data from the pilot program to design a larger study that will tell us how much water people are using and whether water use varies significantly from one part of the valley to another. 

The Water Accounting Project is also driving Water 2066—a community-based effort to create a vision for the Methow’s future.  Water Accounting data will tell us how much water we have to work with so we can generate ideas that support people and the environment. 

Resources:

Water Withdrawal Study (Part 1, Part 2, Part 3) /2011 IFR Database / IFR Database Update Memo