Although the Methow watershed’s April snowpack measurement was at 95% of normal, it was still ahead of last year’s 88%.
Most basins throughout the state had snowpack measurements above normal as of April 1, but the Methow watershed is an outlier, even within the usually snowy Upper Columbia Basin.
In fact, all watersheds within the Upper Columbia basin have a generous snowpack except the Methow, which is at 95% of median. Still, that’s an improvement over last year, when it was just 88%, according to the April 1 Washington Water Supply Outlook Report issued by the Natural Resources Conservation Service (NRCS).
The Omak watershed is at 139% of median and the Sanpoil is at 150%. Precipitation in the Upper Columbia Basin has been 88% of the March average.
With recent temperatures below normal and fresh snow in the mountains, many watersheds are still adding snowpack. Nevertheless, deficits in soil moisture continue to be of concern for spring runoff, since the mountains didn’t receive the typical fall rains and were record-dry when the first snow fell last year, Water Supply Specialist Scott Pattee said in the report.
When snow starts to melt, it soaks into the dry soil before it begins trickling into mountain streams and into mainstem rivers, which much of the state — particularly east of the Cascades — relies on throughout the summer and fall.
Snow depth at Harts Pass has increased by 7 inches since the end of March, reaching 95 inches on April 11. The crucial measurement of snow-water equivalent — the depth of water that would result if the entire snowpack melted instantaneously — is higher than it’s been in a month at Harts Pass, going from 38.6 inches on March 13 to 45.2 inches today, according to NRCS.
Rainy Pass has 73 inches of snow (the same as the end of March), but it’s added about 2 inches of snow-water equivalent, with a reading of 31.3 inches on April 11.
The Methow and Okanogan valleys rely on snowpack to recharge streams and rivers throughout the summer and fall, for household and commercial use, agriculture, fish and recreation.
Early forecasts
It’s still early for a reliable streamflow forecast, since “at times only a few degrees warmer or cooler than forecasted can make or break streamflow predictions,” Pattee said. The report predicts an 81% to 104% chance of average streamflows in the Upper Columbia basin. Runoff in the Methow River at Pateros was 51% of average for March.
Forecasters aren’t pointing to anything out of the ordinary for temperatures in the Northwest from April to June — they predict equal chances of weather that’s warmer or cooler than normal. The forecast is for more precipitation than normal through the end of April, before turning drier than normal heading into summer.
Drought measurements as of April 4 put the western third of Okanogan County in the “abnormally dry” category, which is at the low end of the six-tiered scale used by the U.S. Department of Agriculture for its weekly U.S. Drought Monitor. The scale of drought intensity goes from “none” to “abnormally dry” to four stages of drought — “moderate,” “severe,” “extreme” and “exceptional.” There was no drought intensity in the rest of the county.
Last year at this time, the situation was reversed, with no drought intensity in the westernmost part of the county and abnormally dry conditions in a narrow strip in the Methow. The eastern half of the county was already in moderate drought, with the southeastern corner in severe drought.
