Water Basins
Surface Water Supply Index ( SWSI )

*select region on map to view SWSI for that region

The SWSI is designed for areas that rely on snow melt as the primary source of surface water.
The SWSI accounts for snowpack, mountain precipitation, streamflow, reservoir storage, and soil moisture conditions.
The SWSI has been available in Montana since February of 1990 and is used to evaluate current and seasonal surface water supplies.
It is typically used by irrigators, fisheries personnel, recreationalists, and others who utilize surface waters.

*definition provided by NRCS - national resources conservation service (montana).