Yakima Basin water supply

In October 2025, the Yakima Basin experienced historically low reservoir storage and streamflows after a third consecutive year of drought. We have not experienced a drought like this in over 30 years.  

Water from the basin’s reservoirs ran out on Oct. 6, 2025. Without that stored water, precipitation and flows from the Yakima River would not have been enough for even the oldest water right in the basin. 

These unprecedented conditions required us to restrict all surface water use in the basin to protect the most senior water rights. The restrictions were in place until the end of October, though we assessed conditions each day to determine if some or all water right holders could resume water use.

April 1, 2026 – It is too early to know what water supply conditions will look like in October and how that impacts senior water rights. To be safe, we are preparing for a possible restriction of senior water rights in October 2026. 

Senior water rights may be restricted if reservoir storage is low, and flows in the Yakima River are low. If there are October water restrictions, letters will be sent out to the individuals affected. 

Water restrictions occur each year in the Yakima Basin, especially for junior water rights (priority dates after May 10, 1905).

Timing of restrictions vary from year to year and can occur earlier and affect more water users with each successive drought.

In drought years, senior water rights (priority dates before May 10, 1905) may be restricted after September 30. Also, localized restrictions may occur for junior and senior water right holders that divert from tributaries, when flows drop and hot, dry conditions persist. Letters will be sent to these water right holders and the restrictions will be shown on the map.

The best way to get updates on upcoming restrictions is to check this website frequently.

Water use in the Yakima Basin is restricted during declarations of drought.

When there is abundant rain and snow, all water right holders can use as much water as is permitted by their right. During drought, when surface water is scarce, only the most senior water right holders can use water. The oldest water right in the basin has the legal right to use all their allocated water before the next person in line can access whatever remains. 

This means that when water supplies are low, we must manage water by priority date so there is enough for senior water rights. Ecology is legally authorized to place these restrictions under court order, which is unique to the Yakima Basin and doesn’t happen elsewhere in Washington. 

The Yakima Basin underwent a 40-year legal process to determine who has surface water rights and their order of seniority. This process is known as adjudication. It gives us certainty to regulate water fairly and consistently based on priority date.

In Washington, a drought emergency is declared when water supply conditions are, or are expected to, fall below 75 percent of average, and there is potential for undue hardships due to low water supply. This is done when certain conditions are met (RCW 43.83B). Washington declared drought on April 8, 2026.  A drought declaration does not give direct authority to curtail water use. It does give the opportunity for drought response.

For the Yakima Basin, an emergency drought declaration has been issued every year since 2023.