By Ann McCreary
Weather forecasts calling for a continued cool spring, combined with above-average snowpack in the mountains, means that most of Washington state can look forward to a favorable water supply this summer, according to a state water supply specialist.
Snowpack readings at the beginning of April were 113 percent of normal statewide, with the Methow basin at 129 percent of normal, slightly higher than last year at the same time when the snowpack was 119 percent of normal. The Harts Pass SNOTEL snowpack measuring station at 6,500 feet was at 131 percent of normal on April 9.
The Toats Coulee Creek basin near Tonasket had the most snow in the state from the April 1 snow survey with 203 percent of normal.
A cool spring promotes a normal runoff and sustained flows throughout the summer, said Scott Pattee, water supply specialist with the Natural Resources Conservation Service. “Current soil moisture conditions also point to increased runoff. Most current forecast through mid-April shows most probability of below normal temperatures and above normal precipitation, with a trend towards normal temperatures by the end of the month,” Pattee said.
March precipitation was below normal for the whole state except for the Upper Columbia basin, which includes the Methow Valley and had 133 percent of normal precipitation last month. The Salmon Meadows SNOTEL recorded 243 percent of normal and Omak was 225 percent of normal precipitation.
Summer streamflows “are looking stellar” in Washington, Pattee said, although he warned that streamflow predictions can change with only a few degrees warmer or cooler temperatures than forecasted.
Summer runoff forecast for the Methow River is predicted to be 142 percent of average, and for the Okanogan River is 146 percent of average. That is good news for farmers, fish and wildlife, which all depend on a steady supply of melted snow to fill rivers and streams during the hot, dry summer months.
April – September forecasts for rivers in the Upper Columbia basin range from 118 percent to 153 percent of average, Pattee said. March streamflows on the Methow River, measured at Pateros, were 128 percent of average.
The lowest snowpack readings in the state were 79 percent of normal in the Ahtanum Creek basin near Yakima.