WASHINGTON, April 15, 2014 – Several Northwestern states are expected to have near normal of above normal water supplies, while far less than normal streamflow is expected in some southern portions of the nation, according to report released April 14 by the Agriculture Department.

USDA’s National Water and Climate Center (NWCC) found in its April water supply forecast that March storms increased snowpack in the northern half of the West but did not provide much relief for the dry southern half.

According to the Natural Resources Conservation Service (NRCS), most of Idaho, Montana, Wyoming, and northern parts of Colorado and Utah are expected to have near normal or above normal water supplies, according to the forecast. Far below normal streamflow is expected for southern Oregon, California, Arizona, New Mexico, southern Utah and western Nevada.

NWCC hydrologist Cara McCarthy said early April is commonly regarded as the transition from snow accumulation to snowmelt, making the April water supply forecast of key importance for planning.

“Many water managers, reservoir operators, irrigation districts and hydroelectric power companies make significant strategic decisions based on the April forecasts,” McCarthy said.

McCarthy said that in states where snowmelt accounts for the majority of the seasonal water supply, information about snowpack serves as an indicator of future water supply. Streamflow in the West consists largely of accumulated mountain snow that melts and flows into streams as temperatures warm. NRCS scientists analyze the snowpack, air temperature, soil moisture and other measurements taken from remote sites to develop the water supply forecasts.

For the second consecutive month, many snow telemetry sites in Montana, Wyoming, and parts of Idaho, Washington, and Oregon received two to three times the normal amount of precipitation. The Cascade Mountains in Washington went from extremely dry in January to a normal snowpack currently and Montana and Wyoming snowpack is now at record levels.

“There’s flooding potential in the Missouri River basin,” McCarthy said. “These areas will be most vulnerable if snow melts rapidly during a hot spell, or if there’s extreme rain while the streams are swollen with snowmelt.”


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