Aug. 2, 2001
David Murillo
509-575-5848 Ext. 213

Yakima Basin August Water Supply Forecast

 

The August 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 August 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	-1.525 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 – 37 % of full supply.

The July prorationing level improved slightly from the May, June, and July 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 while July precipitation was only 37 percent of average. The irrigation districts have managed their demands very tightly. 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 August 1 were as follows:

Reservoir	Content (acre-feet)	Total Capacity	Percent of Capacity
Keechelus	46,700	140,3001	33
Kachess	103,524	239,000	43
Cle Elum	120,810	436,000	28
Bumping	27,532	33,700	82
Rimrock	144,279	198,000	73
Totals	442,8452	1,047,9001	42

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