The absence of precipitation in the Lost and Wood river basins this winter has caused officials with the Natural Resources Conservation District to predict water shortages for irrigators this summer.
The April snow survey shows the dry conditions in those two basins “are causing some water supply concerns for irrigators, dryland grazing operations and folks relying on natural streamflow. There will likely be agricultural water shortages in these basins this summer,” State Conservationist Curtis Elke wrote.
The winter proved to be drier than hoped in almost all of Idaho, Elke said. Except for the Clearwater Basin, the snowpack in all of Idaho was below normal on April 1, ranging from 63% to 110% of normal. Total precipitation ranged from 61% to 98% of normal when the snow survey was conducted.
Idaho’s snowpack volume peaked earlier than usual this year. Most of the state’s snowpack was already starting to melt by April 1 in part because the first half of March was “extremely dry over nearly all of Idaho,” according to the report.
But the report says even though winter ended dry, most reservoirs in Idaho are expected to fill because most are on pace with the historic 30-year average storage levels. That indicates normal winter baseflow into reservoirs, Elke said.
Warmer temperatures in March kicked off the melt season a bit early, according to the report, and snotel site data indicates that peak snowpack for the winter was reached in March.
The lack of March precipitation curtailed the snowpack gains that were recorded in February, leaving most Idaho basins with near-normal snowpack levels. But not in the Lost, Wood and Bear river basins. The Little Wood Basin is at 63% normal and the Little Lost Basin is at 80% of normal.
While 2021 isn’t a record low year by any means, and Elke points out snowpack this year “is much, much healthier compared to 2015 or 2001,” the lowest snowpack years so far this century.
The streamflow forecasts for the Salmon and Little Lost basins are predicted to be between 70% and 85% of normal. The Big Lost is expected to be at 51% of normal while the Little Wood is pegged at 43% of normal and the Big Wood at 35% of normal.
The Salmon basin recorded just 47% of normal precipitation in March, according to the report. The Lower-Middle Salmon and the Lemhi sub-basins received more than 50%. The lack of precipitation last month brought the water year precipitation down to 83% of normal on April 1 from 90% of normal on March 1 in the Salmon Basin.
Snowpack in the Salmon Basin remains at 90% of normal, despite very little new snow in March, Elke wrote. The north-south trend exists in the Salmon Basin with the northern Lower-Middle Salmon sub-basin at 99% of normal snowpack, the Little Salmon sub-basin at 96 % of normal and the southern sub basins ranging from 80% to 90% of normal.
Streamflow forecasts are expected to be typical in the Salmon basin, according to the report.
March precipitation in the Lost and Wood basins ranged from 39% to 56% of normal, leaving water year precipitation in the basins between 61% and 73% of normal. And snowpack is below normal, from 67% of normal in the Big Lost and Little Wood basins to 75% to 80% of normal in the Little Lost and Big Wood basins.
Mackay and Little Wood reservoirs are holding about 95% of normal water, according to the report.