Background and Purpose

The Jefferson River Watershed Council (JRWC) is requesting investigation of existing and potential stream and natural spring depletion from groundwater development by exempt and irrigation wells and impacts to groundwater and surface water from changes in irrigation practices or land use.

Agriculture, the primary industry in the Jefferson Valley, is dependent on adequate stream flow or groundwater for survival. The entire population of the area is dependent on groundwater for their drinking water.  Additionally, the Golden Sunlight Mine, a primary employer in the area, is dependent on water from the Jefferson Slough and groundwater for their operation. The Jefferson River has been subject to more stream closures than any other river in Montana and experiences depressed trout populations, due primarily to severe dewatering and elevated temperatures that occur during drought-year irrigation seasons. 

The Montana Department of Fish, Wildlife and Parks has designated the Jefferson River, Pipestone Creek, and Whitetail Creek as Chronically Dewatered Streams. Past studies have shown that groundwater recharge is the predominant source of water for the upper Jefferson River in drought years and that the sources, timing, and quantity of this recharge are very complex. Very low water flows and heavy sediment in the Jefferson Slough appear to be significant contributors to the extensive infestation of Eurasian Water Milfoil (EWM) recently discovered in the lower Jefferson Slough. This infestation appears to be the source of EWM in the Missouri River Basin.

Project Scope

The study area would encompass the Jefferson River valley and adjacent benches from the headwaters of the Jefferson at Twin Bridges to Cardwell, and the lower reaches of the Jefferson River tributaries Pipestone Creek, Little Pipestone Creek, and Whitetail Creek.

GWIP Personnel Assigned:

Andrew Bobst – Team Leader/Hydrogeologist
406.496.4409, abobst@mtech.edu

Publications and Reports:

• UpperJefferson River — GWIP Nomination by Jefferson River Ground Water Study (pdf file)

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