Washington Water Supply

Last revised: July 7, 2017

Watching the water supply

Two years after the “snowpack drought,” water is abundant thanks to a much wetter than normal October to May, including the record wettest October and wet February through April. A cooler than normal October to May would have posted an even colder average temperature, but November was the warmest on record, moderating final numbers.

In some ways this past year has been more unusual than 2015. It will be long remembered. Our friends at the Natural Resources Conservation Service tell us that the rain gauge at Swift Creek south of Mt. St. Helens in Skamania County overtopped at 250 inches this year. The whiplash between the extremes makes life very interesting for water managers all over the east and west. What will the next shoe that drops look like?

Given the abundant water stores, the Water Supply Advisory Committee is going to enjoy a summer break and will next convene in October at the start of the new water year. We’ll still be keeping an eye on water supply until then.

Snowpack | The snowpack has melted away at nearly all stations by now. Just a few stations have remaining snow. As of July 6th, Swift Creek is leading the pack with 34.7 inches of snow water equivalent. Running a close second, Easy Pass in the North Cascades with 32.8 inches.  In third, Paradise at Mt. Rainier at 26.7 inches.

Streamflows | Streamflows are running strong this year. The statewide average streamflow across more than 145 stations is just above normal. Reservoirs west and east of the Cascades are in good shape. Seattle’s combined water storage is well above average, even as demand picks up with the hot weather. Total water supply for the Yakima Basin is forecasted as 108 percent of normal so irrigators will get their full supply.

Groundwater | This spring wheat farmers in Eastern Washington contended with wet, muddy fields, but the good news is that groundwater levels in shallow aquifers have rebounded and then some. The USGS Groundwater measurement well near Dayton in Columbia County is showing water levels significantly above levels recorded historically.

Regional weather | In the tropical Pacific, there are changes since March: what looked like a weak to moderate El Niño is not looking as likely. Though it is bit on the warm side, the eastern tropical pacific has cooled. The forecast: tropical waters will remain a bit on the warm side but not enough to make much difference to the Pacific Northwest. Extended outlooks for the rest of the summer indicate higher probabilities of warmer, drier weather. We can all barely remember what March felt like, right?

For those interested in “when will fall rains start,” it looks like summer into fall might be a bit on the warm side. This time of year can confound forecasts. For now, there is no clear signal when the rains will begin. Looking out the next month or so, the overall circulation patterns appear to be slightly cool and wet.

Water Supply Information




USGS Real time Streamflow Link

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