Recent rains haven't done enough, predicted runoff flows still low

June 12, 2015

from the Columbia Basin Bulletin http://www.cbbulletin.com/434232.aspx Despite recent rains in the Columbia Basin (of which the Kootenai and Moyie Rivers are tributaries), it hasn’t been enough to alter forecasts for low river flows between now and September. Taylor Dixon of the National Weather Service’s River Forecast Center in Portland gave a June 4 teleconference presentation on weather and river flows, and the storyline of the last few months persists. “Temperatures have played the biggest role in things this year,” he said, adding that there was more rain than snow compared to 30-year averages, there was an earlier than normal snowpack melt followed by an earlier than normal runoff. Dixon stressed that the overall precipitation picture since last October was actually close to average, and in many drainages throughout the basin, it was even better than last year’s overall precipitation. “Overall runoff is not far from normal but the timing of it has been abnormal,” Dixon said. Runoffs were higher than normal in most Columbia Basin river drainages up until April, but after that, they dropped precipitously. At The Dalles Dam on the Columbia River, for instance, flows from October through June 3 has been at 102 percent of average, but between April 1 and June 3, flows have been at 77 percent of average. That does not reflect dry conditions west of the Cascades, where record-low volume flows are forecasted through September: 61 percent of normal on the Skagit River; 36 percent on the Dungeness River; 46 percent of on the Cowlitz River; 44 percent on the Lewis River; 59 percent on the McKenzie River; 42 percent on the South Santiam River; 46 percent on the North Santiam River; 50 percent on the Willamette River; and 49 percent on the Clackamas River. The outlook is somewhat better east of the Cascades, largely because river flows are augmented by higher elevation basins in Canada, Montana and Idaho, Dixon said. Flows through September at The Dalles Dam on the Columbia River are expected to be 72 percent of average, a forecast that has not changed since an early May River Forecast Center update. However, Dixon said that unexpected, increased diversions from upstream drainages, for agricultural or other purposes, could lead to lower flows. Flow forecasts for other rivers through September include 91 percent of normal on the Columbia River at Arrow Lakes; 81 percent on the Kootenai River in Montana; 68 percent on the Clark Fork at Cabinet Gorge; 43 percent on the Spokane River (a record low); 79 percent on the Columbia River at Grand Coulee Dam; 72 percent on the Snake River at Shelley; 50 percent on the Snake River at Brownlee Dam; 56 percent on the Snake River at Granite Dam; 33 percent on the Grand Ronde; 38 percent on the John Day River; and 36 percent on the Yakima River (a record low). There is currently a statewide drought declaration in Washington, and drought has been declared in 15 Oregon counties and five Idaho counties. And the National Weather Service’s three-month outlook weather outlook does not indicate there will be a change to the trend. Dixon said there is an above-normal chance there will be above-normal temperatures, but he said the outlook for rain is difficult to pin down, especially with a three-month forecast.