Date of Award:

12-2022

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Civil and Environmental Engineering

Committee Chair(s)

Belize A. Lane

Committee

Belize A. Lane

Committee

Tianfang Xu

Committee

Bethany Neilson

Abstract

The climate in many parts of the Western US is characterized by cold, wet winters preceding long, dry summers. In the absence of precipitation, water supplies in these regions are sustained by melting snow and mountain groundwater. Changes in regional climate can reduce snow accumulation, accelerate melt, and prolong dry periods, all increasing the importance of groundwater on summertime water availability. In mountainous regions with limestone and dolomite geology, bedrock formations can host significant karst aquifers comprising dissolution-enhanced karst conduits which play an outsized and variable role in how precipitation is translated into streamflow. In this study, we considered an intensively monitored watershed in the Bear River Range of Northern Utah with major karst influences to evaluate geologic and climate controls on streamflow patterns. We evaluated water quality and discharge time-series along with model simulations of snow accumulation and melt for six tributary subcatchments, four mainstem subcatchments, and two major springs within the 554 km2 study area across wet, moderate, and dry years. Most subcatchments had clear annual streamflow and water quality response associated with melting snow, but the magnitude of these responses varied by a factor of 10 across the study area. Unlike many snowmelt-dominated mountain watersheds, the variability in response between subcatchments could not be well described by climate conditions or topographic characteristics. We use the diverse streamflow responses to propose a conceptual model of three attributes that can be used to characterize and facilitate understanding and water management of karst- influenced mountain watersheds: conduit flow direction, matrix flow direction, and degree of karstification.

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