Abstract
In 1995, the Montana legislature deemed the upper Clark Fork and its tributaries over-appropriated, and statutorily closed the basin to new water rights above Milltown Dam. The statute, however, makes an exception for ground water. In response to the closure, and prompted by the recent drought, agricultural water users have turned increasingly to ground-water wells and sprinkler systems as more reliable and efficient irrigation methods than traditional flood irrigation from surface-water diversions. The increased crop production made possible by these changes increases water consumption from the basin. New residential and commercial water users likewise may withdraw additional ground water from aquifers in the basin. Because ground water naturally discharges into stream channels, this increased consumption of ground water ultimately decreases streamflow in the Clark Fork. Water-right transfers provide an alternative means to develop new water projects without increasing overall water consumption. Concurrent enforcement of the basin closure statute for all water, whether from surface or subsurface sources, would prevent further river dewatering and protect existing water rights.
Start Date
1-4-2005 9:40 AM
End Date
1-4-2005 10:00 AM
Document Type
Presentation
Ground-Water Pumping & Streamflow Depletion in the Upper Clark Fork Basin
In 1995, the Montana legislature deemed the upper Clark Fork and its tributaries over-appropriated, and statutorily closed the basin to new water rights above Milltown Dam. The statute, however, makes an exception for ground water. In response to the closure, and prompted by the recent drought, agricultural water users have turned increasingly to ground-water wells and sprinkler systems as more reliable and efficient irrigation methods than traditional flood irrigation from surface-water diversions. The increased crop production made possible by these changes increases water consumption from the basin. New residential and commercial water users likewise may withdraw additional ground water from aquifers in the basin. Because ground water naturally discharges into stream channels, this increased consumption of ground water ultimately decreases streamflow in the Clark Fork. Water-right transfers provide an alternative means to develop new water projects without increasing overall water consumption. Concurrent enforcement of the basin closure statute for all water, whether from surface or subsurface sources, would prevent further river dewatering and protect existing water rights.