Date of Award

8-2021

Degree Name

Doctor of Philosophy

Department

Geological and Environmental Sciences

First Advisor

Dr. Donald M. Reeves

Second Advisor

Dr. Mohamed Sultan

Third Advisor

Dr. Duane Hampton

Fourth Advisor

Dr. Lei Meng

Keywords

Unmanned aerial vehicles, fracture spatial clustering, integrated modeling, discrete fracture network, climate change

Abstract

More than 72% of sub-Saharan Africa land surface is comprised of hard rock with fractured rock aquifers supplying water to an estimated 25% of the rural population. Given low porosity and storativity, fractured rock aquifers are particularly vulnerable to stresses such as projected population growth and climate variability. General circulation models of sub-Saharan Africa predict increases in temperature and in occurrences of extreme precipitation trends, such as flooding and drought. Adaptation strategies that promote optimal uses of water resources have emerged, although, most focus exclusively on surface water resources. This project investigates the potential impact of climate change on surface and groundwater resources in the Koumfab watershed (Togo), and the influence of fracture spatial organization on solute transport. Drone surveys of surface outcrops in the study region are used to characterize the fracture network. Fracture network statistics are then used to generate synthetic discrete fracture networks, to better estimate the permeability anisotropy. The numerical hydrologic model of the Koumfab watershed is developed and parameterized using hydrogeologic data from 37 wells in the study region. Historical groundwater level and stream discharge data within the watershed are used to calibrate the numerical model. Future precipitation and temperature data from the Coupled Model Intercomparison Project (CMIP5) are used to force the calibrated hydrologic model. To study the influence of spatial organization on solute transport, synthetic discrete fracture networks with different degree of clustering are generated and transport simulations are performed. The results of transport simulations indicate that particle breakthrough time significantly increases as networks become more clustered. Hydrologic simulations of the Koumfab watershed suggest that groundwater and surface water resources are particularly sensitive to precipitation changes, and a general decreasing trend in groundwater level and streamflow rate is observed.

Access Setting

Dissertation-Open Access

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