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Intrinsic groundwater vulnerability assessments: A review of the state-of-the-art and a statistical approach to incorporating uncertainty into groundwater vulnerability assessments

Date

2019-09-10

Journal Title

Journal ISSN

Volume Title

Publisher

ORCID

0000-0002-1540-488X

Type

Thesis

Degree Level

Masters

Abstract

Groundwater vulnerability assessments, often presented in the form of a thematic map, provide a measure of the relative susceptibility of a groundwater system to contamination introduced at or near the ground surface. However, most groundwater vulnerability assessments rely on deterministic, point estimates based on averaged input parameters, and result in a single output value without any indication of the uncertainty or variation around this value. To facilitate the most effective application and interpretation of groundwater vulnerability assessments, a method for incorporating the uncertainty associated with the natural variation of input parameters into groundwater vulnerability assessments was developed and demonstrated in south-central Saskatchewan. A comprehensive literature review and synthesis, including a review of the conceptual basis of intrinsic groundwater vulnerability assessment methods, a critical evaluation of common and representative methods, and a review of the current research in the field illustrated opportunities for extending the application of these methods as decision support tools. A modified, depth-defined Aquifer Vulnerability Index (AVI) method was developed based on statistically derived, depth-defined hydraulic conductivity distributions generated from hydraulic conductivity data for the Pleistocene-aged glacial till aquitards of the Interior Plains region of Saskatchewan. This modified AVI method was used to produce three sets of vulnerability indices based on the range of probable hydraulic conductivity values, allowing for the pseudo-quantitative assessment of the uncertainty associated with the variability of the input parameter. A final vulnerability map was produced showing the mean (expected) AVI value with an overlay indicating areas of elevated uncertainty. Comparisons of the modified AVI method with a classic AVI assessment revealed the impact of geological controls over groundwater vulnerability assessment results. The methods developed for incorporating and presenting uncertainty in groundwater vulnerability assessments are not limited to local applications of the AVI method, but can be applied to any deterministic vulnerability assessment method where a statistical characterization of the input parameters is possible. Furthermore, valuable and accessible reference information presented here in the form of a hydraulic conductivity database, summary tables, and conceptual models will aid in the effective selection, application, and interpretation of intrinsic groundwater vulnerability assessments.

Description

Keywords

Groundwater vulnerability, Vulnerability mapping, Hydraulic conductivity, Glacial till, Scale effects, Aquifer Vulnerability Index

Citation

Degree

Master of Science (M.Sc.)

Department

Civil and Geological Engineering

Program

Civil Engineering

Citation

Part Of

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DOI

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