Abstract
Population in the Flathead Valley is about 70,000, an increase of more than 25 percent in the last decade. Residents, except for the town of Whitefish, rely on groundwater, primarily from the deep aquifer. The deep aquifer is the most utilized aquifer in the valley, supplying high-capacity municipal and irrigation wells in addition to thousands of domestic wells. The deep aquifer is a thick deposit of gravel and sand, the top of which is 75 to over 400 feet deep and separated from shallow units and the land surface by a thick confining unit. The overlying confining bed is extremely effective at isolating hydrologic stresses in some areas, but not all. Continued growth and localized water-level declines in the deep aquifer have raised concerns about sustainability of the aquifer. Groundwater flow is toward Flathead Lake and flow to the lake is suggested but no direct connection has been confirmed. The degree of connection determines the potential for impact to the Lake by groundwater pumping. Due to the thick confining unit, the degree of groundwater/surface-water connection, if present, is not well understood.
This presentation will focus on hydrologic characteristics of the confining unit and potential interconnection between the deep groundwater flow system and Flathead Lake. The discussion will include geology, aquifer testing, water chemistry, hydraulic characteristics and spatial extent of the confining unit, and water level correlations between the Lake and the deep aquifer.
Start Date
24-4-2015 12:00 PM
End Date
24-4-2015 2:00 PM
Document Type
Poster
Flathead Valley Deep Aquifer development and implications for surface water
Population in the Flathead Valley is about 70,000, an increase of more than 25 percent in the last decade. Residents, except for the town of Whitefish, rely on groundwater, primarily from the deep aquifer. The deep aquifer is the most utilized aquifer in the valley, supplying high-capacity municipal and irrigation wells in addition to thousands of domestic wells. The deep aquifer is a thick deposit of gravel and sand, the top of which is 75 to over 400 feet deep and separated from shallow units and the land surface by a thick confining unit. The overlying confining bed is extremely effective at isolating hydrologic stresses in some areas, but not all. Continued growth and localized water-level declines in the deep aquifer have raised concerns about sustainability of the aquifer. Groundwater flow is toward Flathead Lake and flow to the lake is suggested but no direct connection has been confirmed. The degree of connection determines the potential for impact to the Lake by groundwater pumping. Due to the thick confining unit, the degree of groundwater/surface-water connection, if present, is not well understood.
This presentation will focus on hydrologic characteristics of the confining unit and potential interconnection between the deep groundwater flow system and Flathead Lake. The discussion will include geology, aquifer testing, water chemistry, hydraulic characteristics and spatial extent of the confining unit, and water level correlations between the Lake and the deep aquifer.