Reclamation releases Yakima Basin September water supply forecast

YAKIMA — The Bureau of Reclamation’s September 2023 water supply forecast for the Yakima basin indicates the water supply will provide senior water rights 100% of entitlements and junior water rights 73% of entitlements for the June–September total available water supply. The increase in junior water rights rose slightly from 72% from the previous month.

Prorationing began June 1 and will apply to the June 1 through Sept. 30 irrigation entitlements.

Reclamation manages water in the five Yakima Project storage reservoirs, which are 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 forecast is based on flows and reservoir storage along with estimates of future precipitation, river flows, and irrigation return flows. Other future weather conditions that determine runoff, evaporation, and demand for water are also critical in determining stream flows and water supply for irrigation.

Reclamation provides bi-monthly analyses while proratable supplies are near or below 75% and will continue to inform the public when the rates change. Reclamation provides updated water supply forecasts monthly from March throughout the water year, which is through early October, using the latest data each month to reflect changing conditions.

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