Date of Award

2016

Document Type

Open Access Master's Thesis

Degree Name

Master of Science in Environmental Engineering (MS)

Administrative Home Department

Department of Civil and Environmental Engineering

Advisor 1

David W. Watkins

Advisor 2

John S. Gierke

Committee Member 1

Ann Maclean

Abstract

Approximately 1.2 billion people in the world live in an area facing physical, or absolute, water scarcity (defined as access to less than 1,000 cubic meters of water). This number is projected to increase to 1.8 billion by the year 2025. Thirty-eight percent of the world’s population lives in arid, semi-arid or dry subhumid regions, which translates to a high dependence on the 30% of the world’s freshwater present in the ground. Further, the rate of water use is increasing rapidly – between two and two and a half times that of population growth, over the last century.

In regions such as Kaolack, Senegal, known locally as the Saloum and located in the Sahel, the vulnerability of the local population to water scarcity is well known. Compounding this precariousness are precipitation irregularities introduced by a changing climate, making reliance on historical trends for prediction of future patterns increasingly difficult. In addition, deforestation and over-grazing are reinforcing the damage caused by climate change and threatening the integrity of the hydrologic cycle.

To ensure the continued access to safe and plentiful water to those who rely on groundwater for domestic use, an improved understanding of the factors controlling supply to aquifers in the form of recharge is paramount. An in-depth look at each of the mechanisms contributing to recharge (precipitation, evapotranspiration, and runoff) is essential. When the relative contributions of assorted processes and variables to groundwater recharge are better understood, efforts can be more successfully directed to counter the antagonizing mechanisms compromising the health of the hydrologic system.

In this study, three established methods for estimating groundwater recharge were explored, all of which approached this phenomenon with different assumptions and data requirements. These were compared against a hydrologic simulation model developed over the course of this study which offers the possibility of a more detailed estimate of recharge; this new model provides recharge estimates comparable with the established methods. It can also evaluate changes in the system, such as vegetation and soil type, while also having the potential to directly account for the effects of daily rainfall patterns. Despite challenges in calibration and verification with limited data, the simulation model has the advantage of indicating which features control recharge, as well as providing the opportunity to explore changes in land management and climate change into the future, and their attending effects on recharge.

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