The measurements show a jump from below average levels in the months prior, according to the US Dept of Agriculture’s Natural Resources Conservation Service (NRCS).

Last month, measurements in Idaho showed precipitation ranging from 115% above average in the Bear river basin to 160% in the Selway to Little Lost basins along the border with the state of Montana.

Snowmelt is the prime source of runoff in the western US and is a key indicator of the water supply outlook, depending on drought and soil conditions, for many areas and power generation, such as in Idaho.

Last month, survey data showed snowpack in Idaho to be 85%-100% of average, which was an unexpected improvement from the measurements of 70%-90% in February.

The precipitation levels last month have lifted the forecast for the Snake river to have about average flows. NRCS said that, when combined with reservoir storage, the flow should be sufficient to provide adequate supplies to the south of the state.

The Snake river basin is key to the hydro power output of US utility Idacorp. Last month, Idacorp noted that after poor hydrology in 2007 there had been better precipitation in 2008, which enabled a noticeable improvement in generation – an increase of 11.3% to 6900GWh. The latest NRCS data indicates the potential for further improvement this year.

In a statement, NRCS added: ‘The stimulus precipitation was exactly what was needed to prevent the ongoing downward spiral caused by the mid-winter dry spell.’