Thursday, April 7, 2011

Irrigation outlook

march precipitation boosts snowpack across the state

Boise – The Natural Resources Conservation Service’s snow surveyors recently completed the April 1 snow measurements and found that March’s above average precipitation ensures an adequate summer water supply for Idaho's numerous water users.

“With more snowy days than sunny ones in March, snowpacks increased measurably and now range from 100-140% of average for most Idaho basins,” said Ron Abramovich, Water Supply Specialist with the Idaho NRCS.

Streamflow forecasts also increased. “With the good precipitation in March, most people would have thought the March streamflow volumes would be higher than they were,” Abramovich said.

“But most of the 60 plus stations that we use for water supply forecasting were in the 70-95% of average range.”

That’s because most of March’s precipitation fell as snow in the higher elevations. Streamflow forecasts range from near average in the Salmon basin to 150-160% for southern Idaho's high desert rivers.

What does this mean for Idaho’s water supply? Irrigation water supplies will be ample with most reservoirs holding enough supplies to last through the summer. Water is being released from some reservoirs to make room for the anticipated snow melt.

Most of southern Idaho's reservoirs will fill except for the large storage facilities such as Salmon Falls, Oakley and Bear Lake. However, their water users will still have adequate irrigation supplies based on current storage and projected inflows.

Abramovich added, “How the snow melts and fills our rivers and lakes greatly depends on spring air temperatures and rain.” The three month extended forecast calls for wet, cool weather.

The Snow Survey and Water Supply Forecasting Program is developing a web-based tool that will allow users to access data and perform data analysis. Visit the National Water and Climate Center web site at to try out the tool and provide feedback on the tool’s operation by June 3, 2011.

View April’s full report on snowpack, precipitation, runoff and water supply predictions at and click on the ‘Water Supply’ link.

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