July 6, 2001
David Murillo
509-575-5848 Ext. 213

Yakima Basin May Water Supply Forecast

 

The July forecast of the Yakima Basin water supply outlook indicates a continued, significant water supply shortage for proratable users for the current irrigation season. Non-proratable users will receive a full supply.

Converting the July through September natural flow runoff forecast to total water supply available (TWSA) for the May through September use period gives the following volumes:

Low	-1.478 million acre-ft
Adopted	-1.523 million acre-ft
High	-1.578 million acre-ft

Total demand to be placed against this supply for irrigation, regulation, and flows passing Sunnyside Dam are expected to be much less than the average of 2.5 million acre-feet (normal year).

The total water supply available for irrigation is the sum of natural flow, storage, and return flow less residual storage and flow passing Sunnyside dam. Pro-rationing, which began on May 1, will be at the following rate for the proratable users only:

Adopted Prorationing – 34 % of full supply.

The July prorationing level improved slightly from the May and June levels due to a combination of factors including cooperative water management and favorable natural conditions. May and June were cool overall and received slightly above normal precipitation. The irrigation districts have managed their demands very tightly in May and June. The fisheries agencies have coordinated well with the Bureau to satisfy fish needs with available water from the uncontrolled tributaries. The Bureau, in cooperation with BPA, has been managing the Yakima Project hydro power facilities such that both fisheries and irrigation priorities are met first. The Yakima Field Office will continue to work cooperatively this season with all users to stretch the tight water supply to the greatest extent possible.

Storage Conditions as of July 1 were as follows:

Reservoir	Content (acre-feet)	Total Capacity	Percent of Capacity
Keechelus	83,748	140,3001	60
Kachess	148,704	239,000	62
Cle Elum	216,968	436,000	50
Bumping	34,269	33,700	100
Rimrock	158,240	198,000	80
Totals	641,9292	1,047,9001	61

1Keechelus capacity is currently restricted to 140,397 acre-feet. Normal capacity is 157,800 acre-feet.
2Reservoir content at midnight, July 4, 2001 was 627,912 acre-feet, 60 % capacity, 65% of average