Groundwater Resources of the Jocko Basin, Montana

The Confederated Salish and Kootenai Tribes (CSKT) of the Flathead Indian Reservation, Montana, has articulated a goal of protecting their water resources and related eco-systems for future generations, while supporting tribal economic development as possible.  In support of these goals, the CSKT has embarked on detailed assessment of groundwater resources in the intermontane basins of the Reservation, including the Jocko Basin.   Compared to many groundwater basins of the West, the Jocko Basin remains relatively unexploited, with only limited groundwater pumping at present for community, domestic and irrigation uses.   Basin streams benefit from identified in-stream flow targets to protect aquatic and riparian resources.   To better understand the groundwater resource, and the extent to which it could be developed without adverse impacts to streams, a basin-scale groundwater model has been developed.   Inflow to groundwater associated with agriculture, including canal recharge and deep percolation from irrigated fields, is developed based on simulation output from an independent surface water and farm budget model.  Observed heads and stream gains/losses were used to support model calibration.  Stream depletion analyses demonstrate the sensitivity of streamflow and riparian hydrologic conditions to groundwater withdrawals and provide information to support the management of this resource.