Gallatin River WatershedA complex, yet critical, linkage exists between surface water and groundwater. Surface water percolates through the soil, recharging groundwater, while groundwater can return to the surface through springs and seepage. In the Gallatin Valley, groundwater is strongly connected to instream flows, and maintains streamflow during times of low flow.
The movement of water between streams and groundwater can control the transport and composition of solutes, aquifer recharge, and spatial sources of streamflow. The structure of a watershed determines the method and channel in which water is delivered, which in turn influences the bidirectional movement between surface water and groundwater. Permanent stream gauging stations are in operation on the Gallatin River at Gallatin Gateway and Logan, as well as Bridger and Middle (Hyalite) Creeks . Stream flow at the Gallatin River and Logan varies annually and is highly dependent on mountain snow pack in the Gallatin Watershed. In a report published in 2007, the snow pack in the seven previous years had been below average, resulting in below average stream flow in the Gallatin River and its tributaries. While water recharge from snow and rain naturally augment the aquifer, additional management is needed to offset the impact on the aquifer from the many water withdrawals and uses occurring in the region. The water exchange proposes managed aquifer recharge methods, such as infiltration galleries located in optimal sites, that will help to restore the aquifer and sustain year round stream flows in the local rivers and tributaries. |