Date of Award

Spring 1-1-2013

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Roseanna M. Neupauer

Second Advisor

Roseanna M. Neupauer

Third Advisor

Harihar Rajaram

Fourth Advisor

John Pitlick

Abstract

In regions where growing population and changing climate threaten freshwater supplies, accurate modeling of potential human impacts on water resources is necessary to ensure a sufficient supply of clean water. Stream depletion, the reduction of stream flow due to the extraction of groundwater from a hydraulically connected aquifer, can reduce water availability; thus, accurate modeling of stream depletion is an important step in siting new groundwater wells. Proper estimation of stream depletion requires appropriate parameterization of aquifer and streambed hydraulic properties. Although streambed hydraulic conductivity (Kr) varies spatially and temporally in natural streams, many numerical investigations of stream depletion assume or calibrate for a single representative value of (Kr) . In this work, we use MODFLOW-2000 to demonstrate that ranges of

(Kr) exist to which stream depletion estimations are sensitive and insensitive. We show that the

sensitivity of a model to (Kr) is dependent upon the model input parameters. Considering the uncertainty that is introduced from the assumption or calibration of a parameter, we apply concepts from sediment transport theory to develop modeling methods that more accurately represent the spatial and temporal heterogeneity of the stream channel. We compare stream depletion estimations from various heterogeneous (Kr) scenarios with a homogeneous base case to investigate how the different modeling schemes impact the feasibility of pumping well locations in the aquifer. Modeling patterns of (Kr) heterogeneity significantly alters stream depletion estimations. However, accounting for temporal variations in heterogeneity patterns lessens the degree to which heterogeneity along the stream channel impacts stream depletion estimations.

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