YAKIMA, Wash. – The Bureau of Reclamation’s April 2020 Total Water Supply Available (TWSA)
forecast for the Yakima basin indicates the water supply will fully satisfy senior water rights while the
junior water rights will be limited to an estimated 96% of their full entitlements this irrigation season.
“March precipitation, at 42% of normal, fell far short of expectations. Snow-pack, as percent of average,
has declined about 5% since March 1. The five reservoirs are just over 62% full and filled about as
expected in March”, according to the Yakima Project River Operations Supervisor. “The Yakima Basin reservoir storage is currently 102% of average and the snow-pack is 95% of average.”
Reclamation manages the water in the five Yakima Project storage reservoirs, along with the basin’s
unregulated inflows to fulfill water rights, water contracts and in-stream flow obligations. Water
shortages in the basin are shared equally by the junior water rights, which represent over half of the
water rights in the basin.
Specific water-delivery levels, such as water rights allocations and stream flow targets, will be set,
normally in June, when the Yakima system requires reservoir storage releases to meet irrigation
diversions and river flows. Reclamation will provide an updated water supply forecast and water
allocation each month—at least through July—using the latest data to reflect changing conditions as
The April forecast is based on flows, precipitation, snow-pack, and reservoir storage as of April 1, along
with estimates of future precipitation and river flows. Other future weather conditions that determine the
timing of the runoff and the demand for water also are critical in determining stream-flows, pro-rations
and the extent to which the reservoirs fill.
“We still have several key months ahead of us that can have a big influence on the ultimate water supply
this summer,” says Garner.
For more information, visit Reclamation’s website at https://www.usbr.gov/pn/hydromet/yakima.
The Bureau of Reclamation is a federal agency under the U.S. Department of the Interior and is the nation’s largest wholesale water supplier and second largest producer of hydroelectric power. Its facilities also provide substantial flood control, recreation opportunities, and environmental benefits. Visit our website at www.usbr.gov and follow us on Twitter @USBR.