The Bureau of Reclamation has performed a special mid-June evaluation of the total water supply available forecast for the Yakima basin. The June–September total water supply available provides senior water rights 100% of entitlements and junior water rights 73% of entitlements (a decline from 77%).

Prorationing began June 1 and will apply to the June 1 through Sept. 30 irrigation entitlements. Reclamation will provide bi-monthly analyses while proratable supplies are near or below 75% and will inform the public when the rate has changed.

Reclamation manages water in the five Yakima Project storage reservoirs, which is used along with other unregulated flows, in the basin, to fulfill water rights, water contracts and instream 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. Senior rights will not be reduced this year.

The June forecast is based on flows, precipitation, snowpack, and reservoir storage through June 14, along with estimates of future precipitation, river flows, and irrigation return flows. Other future weather conditions that determine the timing of the runoff and demand for water are also critical in determining stream flows, extent to which the reservoirs fill, and water supply for irrigation.

Reclamation will provide updated water supply forecasts monthly through July using the latest data each month to reflect changing conditions.

For more information, visit https://www.usbr.gov/pn/hydromet/yakima/. 

Original source can be found here