Date of Award:

5-2019

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Geology

Committee

Thomas E. Lachmar

Committee

Dennis Newell

Committee

Robert Q. Oaks, Jr.

Abstract

Groundwater is documented to flow through solution-widened fractures and bedding planes in limestone and dolostone units in low-relief topography. This enhancement, or karstification, is much harder to study in alpine environments like the Bear River Range of northern Utah. This is problematic, due to the fact that the Bear River Range karst aquifer system supplies the City of Logan with a large quantity of water at Dewitt Spring. Furthermore, the karst aquifer sustains the Logan River for much of the year, and may allow groundwater to flow directly in the subsurface to the Cache Valley principal aquifer system.

Flow measurements along the Logan River constrain a minimum volume of 2.32x106 m3 /y (1.88x103 af/y) that could recharge the Cache Valley principal aquifer. Hydraulic characteristics of alpine karst were estimated by analysis of major ions, stable isotopes, and dissolved gases in spring waters. These data reflect quick groundwater flow through caverns, with no evidence for “diffuse” flow anticipated by some to occupy interstitial space. In fact, the oldest reasonable estimated recharge age for groundwater is 70 years. Young recharge, fast flow, and low storage capability indicate that alpine karst aquifers are very sensitive to droughts and that related water resources are vulnerable to longer-term changes in climate.

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