Montanans can expect a mixed bag of water supply and moisture conditions as summer wears on, according to the 2013 Governor’s Report on the Potential for Drought and Flooding, released recently by the Montana Department of Natural Resources and Conservation.
Abundant spring rain has substantially improved growing conditions for grains, hay and other crops, helping to make up for below-average mountain snowpack in the Missouri and Yellowstone basins. Outstanding soil moisture conditions exist in the north-central, central, eastern and southeastern regions of Montana. Reservoir storage in the central and north-central regions remains excellent.
But the Montana Governor’s Drought and Water Supply Advisory Committee also rates the potential for drought-like conditions through August as moderate to high for surface-water uses east of the Continental Divide in the headwaters of the Missouri River, including the Beaverhead, Jefferson, Ruby, Madison and Big Hole rivers and their tributaries.
Likewise, headwaters tributaries of the Yellowstone River – the Shields, Stillwater and Little Bighorn rivers, along with Rock Creek and Red Lodge Creek – are projected to experience surface water shortages.
Counties at risk for low stream flows in the coming weeks include Park, Sweet Grass, Stillwater, Carbon, Yellowstone, Treasure, Musselshell, Rosebud and Bighorn.
West of the Divide, the potential for drought-like conditions through August is rated as low to moderate for surface water uses, with the exceptions of the Bitterroot and Upper Clark Fork river basins and tributaries. Affected counties include Ravalli, Deer Lodge, Granite and Powell, where stream flows are expected to be well below average.
Five counties west of the Continental Divide are identified as moderately dry: Ravalli, Granite, Powell, Silver Bow and Deer Lodge; two others, Missoula and Mineral, are rated slightly dry. East of the Divide, Gallatin and Beaverhead counties are rated moderately dry, while one, Madison, is rated extremely dry.
Six more counties in the headwaters of the Missouri and Yellowstone rivers were rated slightly dry, including Jefferson, Broadwater, Park, Sweetgrass, Stillwater and Carbon. The remaining 40 counties were evenly divided between the near-average and slightly moist categories.
The report concludes, “It is important to remember that low stream flows, wildfire, and other impacts from dry and warm weather are not uncommon from mid-July into late summer in Montana in any given year.”