Water Resources Research Act Program

Details for Project ID 2004MT31B

Defining river recharge and three-dimensional areas of contribution to production wells adjacent to a losing river, Western Montana

Institute: Montana
Year Established: 2004 Start Date: 2004-03-01 End Date: 2005-11-30
Total Federal Funds: $14,743 Total Non-Federal Funds: $35,534

Principal Investigators: William Woessner

Project Summary: This research effort will attempt to determine sources of water collected by municipal wells located immediately adjacent to the Clark Fork River. The sole source Missoula Aquifer has been reported to receive between 50 to 90 % of its recharge from the Clark Fork River (Clark, 1985; Miller, 1991; LaFave, 2002; Pracht, 2001; Land and Water Consulting, 2003). Water levels fluctuate seasonally 10 to 20 ft in production wells and monitoring wells located within 400 ft of the river (Woessner, 1988. LaFave, 2002). Of concern is how both short and long term changes in river quality will impact produced groundwater quality. Such a determination is critical to successfully managing groundwater withdrawals during periods of stream water quality degradation. Potential sources of short and long term impacts include the release of contaminants directly to the river as a result of rail and highway accidents, catastrophic flood events releasing metal contaminants stored in the floodplain and at storage areas near the river, Warm Springs Ponds treatment system failures, Milltown Dam failure, and water quality impacts related to reclamation and restoration of up-stream Superfund sites. Stage and head monitoring, geochemistry studies using ion concentrations and stable isotopes, and three dimensional numerical modeling will be applied to identify water sources to wells located adjacent to the river. In addition, well head mixing ratios will be determined and areas of contributions mapped. Study results will be used to assist water managers; health department officialsl; state, federal and superfund PRPs designing and managing cleanup efforts, to protect public health and safety.