January to May 2025 Edition
Hydrologic Conditions in Washington State, March 2025 By Tom Ring This article is drawn from several sources, especially the state Water Supply Availability Committee (WSAC) and U.S. Bureau of Reclamation. Current Drought Status Officially, the Declaration of Drought Emergency issued in April of 2024 by the Washington Department of Ecology remains in effect until April 15th of this year. At that point, Ecology will either allow the declaration to lapse or decide to renew it in full or in part. That decision will be based on recommendations from WSAC, which meets monthly and includes input from water managers and hydrology and climate specialists across the state. Meetings are open to the public (Department of Ecology - Committees, Boards, and Workgroups). This article documents conditions in mid-March and explores the chances of recovery to non-drought conditions. Images labeled WSAC March 13 are adapted from the presentations to the March 13th WSAC meeting posted at Presentation Materials (Agenda, Ecology, OWSC, NWRFC, USGS, BOR). Drought Classification Criteria In brief, drought in Washington is based on two characteristics:
Washington Watershed Characteristics Watersheds in Washington vary based on their location within the state, the magnitude of demand for instream and out-of-stream uses, and the presence or absence of reservoir storage. Many watersheds are fully dependent on seasonal snowpack accumulation and snowmelt runoff in addition to rainfall. Others rely on a mix of snowpack and reservoir storage. The Yakima basin in particular relies on snowmelt early in the irrigation season and reservoir releases later in the season. Annual water supply is strongly influenced by carry-over storage, which is the amount left in the reservoirs at the end of the previous irrigation season. Current Conditions
Left and below show two different ways of assessing the likelihood of precipitation reaching long term averages.
These two maps (March 13 WSAC) show contributions by storms in late February and early March, but snow water equivalent remains below average to well below average in the northern and central Cascades.
Below: Plots of snow water equivalent for snotel sites representative of northern Cascades, southern Cascades, and the ecologically important Dungeness River in the Olympics. For comparison, the plots include the snowpack drought year of 2015 and the very wet 1997. Adapted from NWCC iMap.
Key observations from the data:
Yakima Basin Conditions Effects of water short years in the Yakima basin are felt unevenly depending on water right priority date and whether storage is physically available:
The WSAC March meeting took particular interest in conditions in the Yakima basin. Reclamation delivers in excess of two million acre-feet of irrigation water and has 1.1 million acre-feet of storage. Each year, full supply depends on snowmelt to supply early season demands and reservoir releases in mid to late summer.
The bottom line for Yakima Project irrigators is:
From March 13 WSAC. Summary
Meditations on Drought
2001 was a classic drought — near record low precipitation accompanied by near record low February streamflow. In contrast, 2015 tracked near normal precipitation most of the winter and had some record high streamflows. Yakima basin reservoirs filled early.
2015 resembled forecasts for future winters in Washington state. Systems that were designed with the expectation that snowmelt would provide for spring and early summer demands for irrigation and fisheries water are not likely to meet needs. The state's drought definition calls out 75% supply, but as 2015 showed, an overabundance of streamflow in winter doesn't provide much help in August. |
Statewide, precipitation and snowpack have lagged below normal over the fall and winter. According to NRCS, the period from January 6 to February 21 was the driest or 2nd driest on record during that time for most SNOTEL stations in Washington. In most years, this period accounts for a substantial portion of annual precipitation and snowpack accumulation. It is unlikely that areas currently below average precipitation will reach normal levels this water year.
Left shows the strong gradient between wet and dry this year. Dark blue indicates areas that have already reached 100% due to winter storms that mostly missed Washington except the eastern portion.
Images on this page from March 13 WSAC meeting Presentation Materials (
Right: 120-day runoff forecast shows ranges from well below average in the north to above average in the south. From March 13 WSAC.
Current reservoir storage in the Yakima basin is the third lowest in the period of record, following only 1994 (the third year of a three-year drought) and 1987. According to Reclamation, there is no possibility that the three upper basin reservoirs will fill this year (Keechelus, Kachess, and Cle Elum), while in the Naches Arm, Rimrock has a possibility of filling and the comparatively small Bumping Reservoir is expected to fill. 2024 was the second straight drought year, and as a result, end of season (carryover) storage was extremely low. From March 13 WSAC.
Washington state has one definition for drought, but in practice, drought can mean very different things. 2001 and 2015 were both considered drought years, but could not have been more different climatically, as shown by February streamflow data (left from March 13 WSAC). Below Adapted from NWCC iMap.
The similarity was low snowpack both years (left). The difference was temperature. Precipitation was ample in 2015 but fell mostly as rain and ran off over the winter. One popular weather blogger objected to calling it a drought given average precipitation and high runoff. As a result, the term "snowpack drought" became popular. In both cases, proratable irrigators received less than half of full supply.
