2019 Water Supply Outlook released
Influenced by an El Nino weather pattern, the 2019 Water Year began October 1, 2018 with near normal or higher than average precipitation across the state. But below-normal precipitation in November and December led to below normal precipitation totals.
As a result, year-to-date precipitation ranges from near normal across the southern border to 60 percent in central Idaho.
According to the Natural Resources Conservation Service (NRCS), current snowpack ranges from a high of 120 percent of normal in the Owyhee basin to only half of normal in the central mountains.
Reservoir storage is in good shape. Most reservoirs report average storage or higher. About half of winter precipitation is yet to come.
In eastern Idaho, water year-to-date totals are 70 to 85% of average. Because reservoir storage was not as high as last year, NRCS says more snow and greater streamflow volumes will be needed to meet marginal irrigation demands.
In the upper Snake region, December precipitation was just 54% of average. January snowpack was 79% of normal above American Falls Reservoir. Reservoir storage ranged from 154% at Jackson Lake to 108% at Grassy Lake. Streamflow forecast on the Snake River near Heise indicates about 80% of average streamflow.
Elsewhere, the Bear River Basin is currently at 87% of normal snowpack and the Salmon River basin at 73%.