Water forecasts are plentiful, on both sides of the state line

DRIGGS — Idaho water forecasters collect a large amount of data about the upcoming water season, but this spring their outlook had a fairly simple title: “Water, Water Everywhere.”

Streams could be flowing at nearly three times their average flow this spring, thanks to above average snow pack and higher than normal precipitation. That situation is fairly widespread across the state, and in Wyoming as well.

The May streamflow forecasts from the Idaho National Resource Conservation Service (NRCS) call for extremely high volumes ranging from 150 to 270 percent of average from the Payette basin to the Upper Snake, and from the Middle Fork Salmon River to the Bruneau River across to the Bear River basin. The Clearwater streams are forecast around 115 percent of average and amounts increase to 145 percent for Idaho’s panhandle rivers.

Based on that information, Idaho’s problem is not having enough water, it’s having nowhere to put it.

“The challenge this year is not too little water – as all of Idaho’s 2,000-plus lakes and reservoirs will fill this year,” said Ron Abramovich, Water Supply Specialist for NRCS Idaho. “Rather, the concern is limited storage space if inflows continue to exceed outflows and fill the little remaining storage space.”

Idaho NRCS recently released the fifth water supply outlook report for this water year. (Water years start in October) Precipitation since the water year started last fall is above, even well above average, across the state. The lowest amount is in the Clearwater basin at 123 percent of average and the highest is in the Little Wood and Big Lost basis at 182 percent of average.

The highest snow packs in the state are twice normal in Idaho’s central mountains. The snow pack in the Big Wood basin above Hailey is 215 percent of average and record high since records start in 1961. The Little Wood and Big Lost are not far behind their record high years. Across southern Idaho the snow pack ranges from 140 to 180 percent of median. The exception is the Owyhee basin at 119 percent of median. Basins north of the Salmon River basin are about 115 percent of median. Even the lower elevations in eastern Idaho still have a good snow pack that is 185 to 200 percent of median in the Willow, Blackfoot and Portneuf drainages.

Across the Idaho/ Wyoming border April precipitation totals were 150 to 160 percent of average. Precipitation numbers varied between near 250 percent of normal over the Tongue River Drainage (north central Wyoming) to near 110 percent of normal over the Lower Green Basin (southwestern Wyoming). Current water year (October 2016 – April 2017) precipitation across Wyoming is averaging 140 to 150 percent of average.

Mountain snow pack across Wyoming was 125 to 135 percent of median by early May. Snowpack “water” numbers and/or SWEs were the highest across basins in central Wyoming (Wind, Upper Green, and Sweetwater) — varying between 190 to near 230 percent of median. SWEs across basins in southeastern Wyoming were 85 to near 100 percent of median.

Above to much above normal (160 to near 175 percent) snowmelt streamflow volumes continue to be expected across almost all major basins across Wyoming. Well above average (180 to 250 percent) snowmelt streamflow volumes are still expected across the Snake, Wind, Sweetwater, Shoshone, and Upper Green Watersheds. The Little Snake, Upper North Platte, and Laramie Basins are forecast to have slightly below to slightly above normal streamflow volumes during the upcoming snowmelt season.

Reservoirs storages across Wyoming remained above average at 125 to 135 percent for May.

This article was originally published in the Teton Valley News. Is is used here with permission.