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  It limits water withdrawn for those uses to 2 cubic feet per second (cfs) from each of seven river reaches in the Methow basin (“the Reservation”).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 from local water systems 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’s voluntary metering program data will help us better understand how much water local households actually use so we can refine the water-use estimate. 

Then what?

Data from the MWC’s 2020 voluntary metering pilot program will guide the council in developing a larger metering program and creating a work plan for refining and validating water-use estimates.  A reliable use estimate will enable the MWC to account for remaining reservation quantities available to support Okanogan County water availability determinations.

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

 

 

Smart Meter Sign-up 

The MWC is creating a list of landowners interested in having smart water meters installed as part of a voluntary metering program.  Meters will be installed  at no charge and read remotely.  The data will help us understand how much water residents use so we can better understand how demand will change over time.  Click here for a flier  about the Metering Program.  Click here  to email us if you are interested in participating. 

 

Last updated September 14, 2020

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201 WA 20 (Community Center Basement) / PO Box 1212    Twisp, WA  98856

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