Date of Award

5-2015

Degree Name

Doctor of Philosophy

Department

Geosciences

First Advisor

Dr. Duane R. Hampton

Second Advisor

Dr. Mohamed Sultan

Third Advisor

Dr. Daniel P Cassidy

Fourth Advisor

Dr. Jonathan W Peterson

Keywords

Slug tests methods, unconfined aquifers, slug size, Bouwer and Rice, hydraulic conductivity

Abstract

Slug test methods are used to determine in situ aquifer hydraulic conductivity (K) more quickly and economically than a pump test can. This study compares slug test methods for unconfined aquifers, looking at how to conduct a test using a physical slug, and at different analysis methods including Bouwer and Rice (1976), Kansas Geological Survey (KGS 1994), Hvorslev (1951) and Dagan (1978). Questions that motivated this study include: How well does the Bouwer and Rice method work? What is the most effective way to conduct a slug test? Does using a large physical slug relative to the well diameter and volume yield better results than a small slug? Do large initial water level displacements produce better results than small displacements?

Ten wells were slug tested at two sites: a 2.00 m diameter culvert installed vertically in a 2.28 m deep hole and backfilled with uniform sand, and a natural unconfined aquifer. All wells were 0.050 m in diameter, and were tested using two sizes of slug rods, one that was half of the well diameter, and the other was three quarters of the well diameter.

K values calculated from tests at both sites show that the Hvorslev values are 37 percent higher than the Bouwer and Rice results. Bouwer and Rice, Dagan and KGS K values are noticeably lower than Hvorslev Ks; the difference is statistically significant.

Hydraulic conductivity values obtained from tests using a large slug rod are 1.5 times larger than Ks obtained using a smaller slug rod, regardless of analysis method chosen. The size of initial water-level displacement was positively correlated with calculated K values for tests performed using the large slug but not for tests using the smaller slug. The question “Do large initial water level displacements produce better results than small displacements?” remains unresolved.

Access Setting

Dissertation-Open Access

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