Washington Water Supply

Last revised: May 10, 2017

Watching the water supply

Our chilly, rainy, and snowy winter has turned into a chilly and rainy spring. Abundant precipitation has set us up for a strong water supply in late spring and summer, but it also has caused problems with flooding in parts of the state. The weather is expected to stay relatively cool and wet as we inch toward summer, although there is a possibility of warm and dry El Niño conditions in our future. Overall, water supply forecasts are looking good.

Let’s take a look at what’s going on:

Status of supplies

Weather and outlook | The cool and rainy spring continues. Averaged statewide, December through March temperatures have been cooler than normal. It was also wetter than normal from February through March. We’ve had lots of precipitation, often in record amounts and with high frequency. For example, SeaTac airport had measurable precipitation 46 out of 54 days (February through March), which is about 85 percent of the time.

Our winter and spring have been pretty different from the rest of the county:

Regional Climate Center map of Departure from Normal Temperature Year to date

In the coming weeks, climate forecasting models suggest we can expect to continue this pattern of wet and slightly cool conditions. Longer-term forecasts (June through August), indicate higher chances of warmer weather, with conditions drying out on the west side of the state. Early fall (September through November) is currently expected to be slightly warm and dry.

After our La Niña winter, climate experts say there’s an indication we may experience a weak-to-moderate El Niño event in the tropical Pacific. We won’t know that with certainty for a few months, but it could be significant enough to impact our weather in the Pacific Northwest.

Snowpack | The state continues to do well with its snowpack. We and other agencies gauge snowpack in terms of its water equivalent, or the amount of water contained in the snow, compared to average for a particular day. Measurements are made at mountain sites across the state. This is how things are stacking up for our snow water equivalent:

  • We’re currently at 128 percent of normal
  • In 2016 at this time, we were at 90 percent of normal
  • In 2015 (a record-setting drought year) at this time, we were at 23 percent of normal

Most of our basins have hit their peak snowpack levels and spring meltoff is expected to begin soon.

River and streams | If you’ve visited a river or stream recently, chances are it was flowing at near- or above-normal levels. Of the 149 stations measuring streamflow in Washington, only 2 are below normal. The east side of the state is experiencing its wettest water year (October thru September) on record. The region has received about twice its average winter precipitation at this point, which is contributing to flooding and other issues. Some rivers in northeast Washington are reaching their highest flows on record.

Agriculture | There’s good news for farmers who depend on the U.S. Bureau of Reclamation’s five reservoirs in the Yakima River basin. Reclamation recently released the May water supply forecast that indicates a full water supply for both senior and junior water users this irrigation season. Farther to the east, soggy soils have delayed farmers from working in the fields. However, abundant soil moisture will help plants endure the arid time of year.

Drinking water | Water suppliers for our biggest cities are in good shape.

Water Supply Information




NRCS Current Snow Water Equivalent (SWE) % of Normal

2016 Spring Update: Groundwater Level/Storage Response in Washington State