Title
Defining River Recharge and the fate of arsenic in the shallow groundwater system adjacent to a losing river, western Montana
Abstract
The Missoula aquifer is the source of water for over 57, 000 residents of the Missoula valley. This sole-source aquifer is unconfined and coarse grained, and the Clark Fork River is perched above the aquifer in the Missoula valley. The Clark Fork is a losing river, and anywhere from 50% to over 80% of the recharge to the aquifer comes from the river. The source of water input to the Missoula aquifer, and the associated flow regimes are not completely understood. The objective of this study is to identify the source of water for the Missoula valley aquifer, and to quantify the flow regimes of those sources. Of particular interest is whether arsenic is present in the surface and groundwater systems, and how it moves through these systems. Water temperatures measurements, water chemistry (especially arsenic and oxygen isotopes), and hydrological data (such as specific conductance and dissolved solids), will be used to characterize the mixing of surface water with the underlying aquifer, this knowledge will be valuable in assessing the impacts of any possible future contamination of the Clark Fork River on water quality in the Missoula valley aquifer.
Start Date
1-4-2005 1:00 PM
End Date
1-4-2005 3:00 PM
Document Type
Poster
Defining River Recharge and the fate of arsenic in the shallow groundwater system adjacent to a losing river, western Montana
The Missoula aquifer is the source of water for over 57, 000 residents of the Missoula valley. This sole-source aquifer is unconfined and coarse grained, and the Clark Fork River is perched above the aquifer in the Missoula valley. The Clark Fork is a losing river, and anywhere from 50% to over 80% of the recharge to the aquifer comes from the river. The source of water input to the Missoula aquifer, and the associated flow regimes are not completely understood. The objective of this study is to identify the source of water for the Missoula valley aquifer, and to quantify the flow regimes of those sources. Of particular interest is whether arsenic is present in the surface and groundwater systems, and how it moves through these systems. Water temperatures measurements, water chemistry (especially arsenic and oxygen isotopes), and hydrological data (such as specific conductance and dissolved solids), will be used to characterize the mixing of surface water with the underlying aquifer, this knowledge will be valuable in assessing the impacts of any possible future contamination of the Clark Fork River on water quality in the Missoula valley aquifer.