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Clearwater basin level overall above average

April water supply outlook:

In its fourth water supply outlook for the year, the Natural Resources Conservation Service reports Idaho’s mountain snowpack ranges from 95 to 125 percent of normal for most of the state.

“Above normal March precipitation across the state put the icing on the cake in terms of providing adequate stream flows this year,” said Ron Abramovich, water supply specialist with the Natural Resources Conservation Service. “It was just what we needed to nearly guarantee this year’s water supply for the numerous users across the state.”

Temperatures at higher elevations were cold enough to allow most of the moisture to fall as snow which added more water to the mountainous snowpack to melt later this spring. In the lower elevations, the March rains were very beneficial by increasing soil moisture, improving rangeland conditions and generating lower elevation streamflow across the state.

Current streamflow forecasts are near normal across the state, 90 to 115 percent of average.

“The final piece of the water supply picture is spring precipitation,” said Abramovich. “As we have learned in the past, spring precipitation can make or break our streamflow forecasts. More precipitation is still needed this spring.”

Clearwater River Basin

Within the Clearwater River Basin, precipitation throughout the month of March was generous, with the Clearwater basin as a whole receiving 136 percent of average monthly precipitation. Individual basins ranged from a low of 122 percent of average in the Selway, to a high of 157 percent in the Lochsa drainage.

Water year-to-date precipitation totals have been helped substantially by the very wet February and March and now sit at 107 percent of average for the Clearwater as a whole, and range from a high of 115 percent in the Lochsa to a low of 105 percent of average in the Selway.

Snowpack numbers across the Clearwater basin are very consistent and nearly right on the median, with the Clearwater as a whole having 102 percent of normal snowpack.

Individual basins range from a high of 104 percent for the North Fork of the Clearwater and the Selway, to a low of 101 percent for the Lochsa River.

As a result of the substantial March precipitation and improvements in the snowpack percentages relative to the median, all projected streamflow volumes have increased since the March 1 forecasts.

April to July and April to September inflows to Dworshak are forecasted to be 111 percent of average, while the Selway and Lochsa are forecasted to have 105 percent and 107 percent of average, respectively. The Clearwater at Orofino is projected to have 106 percent of average flows, while further down the Clearwater at Spaulding is forecasted at 108 percent of typical April to July volumes. With the NOAA Three-Month Outlook showing an increased probability of above average temperatures recreational boaters could have a great early boating season on the Lochsa and Selway.


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