Electronic Theses and Dissertations

Identifier

6486

Author

Kushal Regmi

Date

2019

Date of Award

7-30-2019

Document Type

Thesis

Degree Name

Master of Science

Major

Civil Engineering

Concentration

Water Resources Engineering

Committee Chair

Claudio Ivan Meier

Committee Member

Roger W. Meier

Committee Member

Farhad Jazaei

Abstract

Describing surface-groundwater flow interactions along rivers requires a good understanding of Ksat, the saturated hydraulic conductivity of the streambed. However, its spatial variability is huge, so that measurements are needed at multiple locations and depths. Because of this, most methods for in-situ estimation ofKsatare either too expensive or time-consuming to capture the detailed behavior ofKsatover a reach in an affordable manner.Current research on the hyporheic zone and surface water - groundwater interactions makes extensive use of PVC minipiezometers as an inexpensive method to sample piezometric levels, water quality, organisms, etc. As a result, it has become popular to also use them for conducting injection or slug tests to determineKsat, due to their ease of application and affordability. However, the field data obtained in this way are most often analyzed using equations based on the Bouwer and Rice (1976) method, originally developed for completely or partially penetrating wells. These are much larger than typical minipiezometers, and have larger screens, suited for testing aquifers with lowKsatvalues (< 10-3 cm/s). This method and its posterior modifications have not been fully validated for small-diameter PVC minipiezometers; this is clearly reflected in the fact that different equations give widely differentKsatvalues when applied to the same field-collected data.We developed a laboratory apparatus to independently measureKsat, with two different approaches, for a range of sediment samples of increasing permeability (10-2 cm/s to 10 cm/s). We first used it as a large-scale permeameter to obtain what we consider to be our trueKsatvalues, and then conducted injection tests using minipiezometers without disturbing the samples. We conclude that the different equations available in the literature for estimatingKsatfrom minipiezometer data do a poor job over our range ofKsat. Also, the available equation for calculating shape factors for partially and completely penetrating wells does not work for this case, as the screens are very different. Thus, new equations need to be developed for determiningKsatfrom minipiezometer data.

Comments

Data is provided by the student.

Library Comment

dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.

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