We closely monitor Washington’s water supply in partnership with other agencies and organizations. Our state’s water supply includes rivers, streams, lakes and springs, and groundwater. These sources provide drinking and irrigation water, fish habitat, and other important benefits.
Here's our latest report on statewide water supply conditions.
Watching the water supply
Conditions as of June 14, 2018
While we entered May with a healthy snowpack, recent warm and dry weather has accelerated snowmelt in the Pacific Northwest. As of June 1, only 25 of 72 snow-measuring SNOTEL sites had snow remaining. The uncharacteristically rapid snowmelt set records in northeastern Washington, northern Idaho, and western Montana.
Rapid snowmelt means less snowpack to supply our rivers and streams through the summer. Both the Natural Resources Conservation Service’s and National Oceanic and Atmospheric Administration’s river forecasts now indicate below-normal streamflows for June through August.
May was remarkably dry, particularly on the west side of the state. The west Olympic coast experienced its driest May on record and all areas west of the Cascades were much below average. Hoquiam received a mere 0.35 inches of rain (average is 3.29 inches). Bellingham received a record low 0.17 inches (average is 2.48 inches). The weekend of June 8 to 10 brought some welcome relief, especially to the Olympic coast, with the Quillayute airport breaking a one-day precipitation record for June 8 with 1.52 inches of rain.
On the east side, conditions were relatively normal, except for the southeastern corner of the state, which saw slightly above-average precipitation.
Despite more recent cool and wet weather on both sides of the state, much of Washington is experiencing a longer-term precipitation deficit. The US Drought Monitor, one of the tools we use to assess water supply, now classifies western and south-central Washington as abnormally dry.
For Washington state, May 2018 was the second-warmest May ever recorded and the warmest since 1958. Temperatures averaged 5.8 degrees above the 1981-2010 normal.
After a cool reprieve during the June 8 to 10 weekend, the weather is expected to return to warmer and drier-than-normal conditions over the next two weeks. NOAA’s Climate Prediction Center near-term precipitation outlook is for below-normal precipitation and above-normal temperatures. Higher odds for warmer, drier weather are expected to continue through the summer — which is Washington’s warm and dry season.
This winter’s favorable snowpack led to favorable predictions for April through September runoff from snow-fed rivers. Our recent warm temperatures, however, led to a disproportionate share of runoff to occur earlier than normal and — importantly — before it is typically needed. Runoff for summer may be lower as a consequence.
Over the past week, 40 to 65 percent of our rivers have been flowing at below-normal levels (below the 25th percentile). Low flows are especially prevalent on the west side of the state.
In southwest Washington, we are regulating water users in the Chehalis River basin to protect senior water rights and adopted instream flows.
Irrigation and storage reservoirs
In the Yakima River basin, the U.S. Bureau of Reclamation operates five reservoirs to store water for agricultural irrigation and fisheries. The current total storage of all five reservoirs is about 110 percent of average or about 1 million acre-feet of water.
In early June, Reclamation revised its forecast for total water supply available in the Yakima basin to 96 percent and provided a special release of stored water to benefit seaward migration of salmonid smolts.
West of the Cascades, the city of Seattle stores water on the Cedar and South Fork Tolt rivers. Their reservoirs are currently full, filled by melting snow and some minor precipitation. Lack of spring precipitation has also led to increased water demand as dry weather stresses yards and landscaping.
Storage conditions for other reservoirs in Washington are available at the NRCS interactive mapping tool.
We are convening the Water Supply Availability Committee, a group of water supply experts, in late June to assess statewide conditions. Look for an update to this page then.