Title
Patterns of Ground-water Fluctuations in Aquifers: Natural & human-influenced ground water–surface water interactions in the Clark Fork River basin, Montana
Abstract
The patterns of water-level fluctuations in wells were analyzed by averaging monthly water-level data for more than 100 wells with multi-year data. Long-term monitoring of water levels in wells shows that two fundamental patterns of seasonal fluctuations are common in the Clark Fork River basin. The most common pattern is a seasonal response to irrigation and canal leakage. Less common is the runoff response–where short-term spring meltwater runoff is mimicked in ground water.
An irrigation response has a springtime water-level rise that is maintained through the irrigation season and declines through winter. Runoff responses are common near major and minor streams and in the canyon reaches of the Clark Fork River. In these areas ground water rises during flood stages, and falls quickly as flood seasons pass. The Missoula valley shows a different runoff pattern, in that water levels slowly decline throughout the summer and fall, reflecting a spreading pulse of recharge water from the Clark Fork River.
The ground-water level data shows that the use of the extensive network of irrigation canals through the Clark Fork River basin has profound effects on ground water. Irrigation maintains, and in fact creates, high ground-water levels in aquifers that range from a few feet to a few hundred feet in depth. The ground water, in turn, discharges to surface water, affecting surface-water flows, probably on seasonal time-scales. Future changes in irrigation practices and patterns should be expected to change seasonal ground water levels.
Start Date
1-4-2005 1:00 PM
End Date
1-4-2005 3:00 PM
Document Type
Poster
Patterns of Ground-water Fluctuations in Aquifers: Natural & human-influenced ground water–surface water interactions in the Clark Fork River basin, Montana
The patterns of water-level fluctuations in wells were analyzed by averaging monthly water-level data for more than 100 wells with multi-year data. Long-term monitoring of water levels in wells shows that two fundamental patterns of seasonal fluctuations are common in the Clark Fork River basin. The most common pattern is a seasonal response to irrigation and canal leakage. Less common is the runoff response–where short-term spring meltwater runoff is mimicked in ground water.
An irrigation response has a springtime water-level rise that is maintained through the irrigation season and declines through winter. Runoff responses are common near major and minor streams and in the canyon reaches of the Clark Fork River. In these areas ground water rises during flood stages, and falls quickly as flood seasons pass. The Missoula valley shows a different runoff pattern, in that water levels slowly decline throughout the summer and fall, reflecting a spreading pulse of recharge water from the Clark Fork River.
The ground-water level data shows that the use of the extensive network of irrigation canals through the Clark Fork River basin has profound effects on ground water. Irrigation maintains, and in fact creates, high ground-water levels in aquifers that range from a few feet to a few hundred feet in depth. The ground water, in turn, discharges to surface water, affecting surface-water flows, probably on seasonal time-scales. Future changes in irrigation practices and patterns should be expected to change seasonal ground water levels.