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A century of groundwater storage variability in transboundary aquifers in Africa’s Sahara

Authors: Aondover Tarhule*, SUNY Binghamton, Emad Hasan, Department of Geography, Binghamton University (SUNY), New York
Topics: Water Resources and Hydrology, Earth Science, Spatial Analysis & Modeling
Keywords: Africa, water resources, Sahara, Satellite Remote Sensing
Session Type: Paper
Presentation File: No File Uploaded

This study, reconstructs 100+ years of groundwater storage variability and changes in seven major transboundary deep groundwater aquifers across the African Sahara in response to natural hydroclimatic cycles. The study employs satellite-based observations of terrestrial water storage (TWS) estimates from GRACE (Gravity Recovery and Climate Experiment) Satellite RL06 and precipitation data from the Integrated Multi-satelliE Retrievals for GPM (IMERG) product. Satellite observations were used to scale (extrapolate) the TWS estimates from two main groundwater models: the WaterGAP hydrologic model and the PCR-GLOBWB model, and precipitation data from the GPCC precipitation product for the period 1901 to 2016 using an autoregressive model with exogenous terms. To understand the hydroclimatic drivers that explain TWS variability, ensemble TWS estimates were analyzed in association with 6 hydroclimatic indices. First we, performed a partial least square analysis with principal component regression to identify the main hydroclimatic drivers to TWS variability. Then we analyzed the mode of the variability in the total signals from TWS and the hydroclimatic indices using continuous wavelet transform and applied a cross-wavelet analysis to identify the phase-correlation between TWS and different hydroclimatic signals. Finally, we calculated the relative contributions of different climate drivers in modulating the recharge/discharge cycles in each aquifer. This study presents a comprehensive hydroclimatic evaluation of groundwater status across the Sahara’s major groundwater aquifers. Information concerning groundwater variability in Africa is required for better projections and planning of the continent’s inadequate freshwater resources.

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