Washington’s water supply outlook
Washington’s water supply outlook
Where did the snowpack go?
It’s been a rollercoaster of a year so far for the state's water supply. A dry winter had us worried about snowpack until an unseasonably cold spring left the state with a surplus. Average statewide temperatures October through April were below normal, ranking as 48th coldest in the state’s recorded history. Just when we were ready to breathe a sigh of frost-breathed relief, a sudden heat wave in May caused an early snowmelt. Snow-fed rivers are raging now, but the forecast is not optimistic.
Snowpack in Washington peaked on April 23, about two weeks later than usual, at 111% of normal snow water equivalent statewide. The snowpack has gone downhill ever since, as rapidly warming temperatures brought on a strong snowmelt. In 18 days (May 1-18), 34,445,826 acre feet of water stored in the snow melted down to 17,376,564, a loss of almost half the snowpack in state watersheds. Many SNOTEL stations — which measure snowpack — experienced record rates of snowmelt in May.
Where did all of that water go?
A lot of the water went into saturating soils left thirsty by below-normal precipitation this past winter, resulting in major improvements to soil moisture, especially in North Central Washington. Once soil saturates, more of the melting snow finds its way into rivers and streams.
Snow-fed rivers have been running strong throughout May. Forecasters at the National Weather Service predict that May runoff for many rivers will be as high as 182% of normal. Half of the monitored locations in the state are likely to exceed 125% of normal. Unfortunately, the early snow melt, coupled with low precipitation forecasts, means there will be less water to meet both instream and out-of-stream needs over the summer.