Dam release and monsoon controlled recharge and drawdown of riparian aquifers, Dolores River, Colorado

Authors

  • Melissa J. Clutter Fort Lewis College

Keywords:

hydrology, hydrogeology, Dolores River, aquifer

Abstract

The Dolores River in Southwestern Colorado is a mountain stream in southwestern Colorado. The semi-arid environment downstream of McPhee Reservoir has a low annual precipitation and a high inter-annual variation. The impoundment of McPhee Dam along the Dolores River has affected the duration and magnitude of peak discharge events, which, in turn, has had downstream impacts. Few published studies have quantified groundwater dynamics in riparian aquifers and dam controlled streams, and this study furthers the knowledge in this field. Three study sites along the Dolores
River, one upstream of McPhee Reservoir and two downstream, were analyzed in this study using a transect of three piezometers at each study site. Piezometers were installed 2-3 m below the surface, and were observed from May to October 2010. All observed piezometer levels downstream of McPhee Reservoir resembled the dam release hydrograph. The duration and magnitude of high flow events were the key factors in effective recharge of the riparian aquifers. Longer duration dam releases created higher groundwater levels and more gradual drawdown times than shorter duration monsoon precipitation events of equal magnitude. In addition to these large scale recharge events, daily water level variations of 2-5 cm were observed in each well. These well variations are thought to be related to significant diurnal air temperature fluctuations and associated evapotranspiration. The measurements obtained from this study provide important information regarding the effects of dam management on groundwater levels in riparian aquifers. This information will become increasingly critical with anticipated climate change in the region.

Faculty Mentors: Gary L. Gianniny and Cynthia Dott

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Published

2019-01-06

Issue

Section

Natural Sciences