JEFFERSON RIVER GROUNDWATER/SURFACE WATER HYDROGEOLOGIC STUDY
Upper Jefferson Valley, Montana
This study was performed on behalf of the Jefferson River Watershed Council and Trout Unlimited to define the groundwater/surface water interaction in the Waterloo area of the Jefferson River. Three major irrigation ditches are in this reach of the river, with two perennial spawning streams, Willow Springs, and Parson’s Slough, located in the north-central portion of the study area. Specific goals of the project were to define the nature of water movement through the study area and the interactions between the Jefferson River, spawning tributaries, local irrigation ditches, mountain recharge, and groundwater flow. The project was completed using a combination of historical data review, groundwater characterization, surface, and stream flow monitoring and gauging. The groundwater monitoring was designed to characterize aquifer conditions in the study area and the interaction with surface water. The groundwater monitoring network consisted of 13 private wells and 22 piezometers located throughout the study area. Data collection consisted of groundwater depths, groundwater elevations, and field and laboratory water quality.
Surface water monitoring was conducted in conjunction with the groundwater study to assess interactions between stream and river flow conditions and their velocities, and water quality. Multiple synoptic runs were conducted throughout the life of the project. The field methods utilized to collect surface water data consisted of staff gauge readings, in-stream flows and stilling wells equipped with Aqua-rods. WET personnel also conducted surface water monitoring of ditch headgates associated with the JRWC Drought Management Plan during this time.
The project results were interpreted and compiled into a detailed report concluding that a complex connection exists between groundwater, surface water and irrigation systems throughout the study area. The groundwater study showed a significant amount of groundwater/surface water interaction throughout the study area, with strong relationships between shallow groundwater, irrigation practices, tributary flows, and rivers flows. Based on the project outcome, WET developed a series of recommendations for use by the project stakeholders and decision makers to better understand the Jefferson River hydrologic system and aid in future land management practices.