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Tools to reconstruct past and project future groundwater levels to inform groundwater resource management in sub-Saharan Africa

IWRA 2020 Online Conference - Addressing Groundwater Resilience under Climate Change
THEME 1. Groundwater Natural Resouces Assessment Under Climate Change
Author(s): Matthew Ascott, David Macdonald, Emily Black, Anne Verhoef, Pascal Nakohoun

Dr. Matthew Ascott
British Geological Survey
United Kingdom

Dr. David Macdonald
British Geological Survey
United Kingdom

Prof. Emily Black
University of Reading
United Kingdom

Prof. Anne Verhoef
University of Reading
United Kingdom

Mr. Pascal Nakohoun
Direction Générale des Ressources en Eaux
Burkina Faso

Keyword(s): Groundwater, modeling, Africa, groundwater level reconstruction, groundwater level projections, water resource management


(a) Purpose or objectives and status of study or research hypothesis

Groundwater has the potential to support climate change adaptation in sub-Saharan Africa. However, much of the continent is underlain by low storage aquifers that can be susceptible to changes in climate, land use and abstraction. The objective of the study was to develop modelling tools to support sustainable development of groundwater resources in these hydrogeological settings.
Models that simulate long-term observed groundwater levels (gwls) can be used to: reconstruct gwls prior to observations to help contextualize current groundwater status; and project future changes in resource under environmental change.

(b) Key issue(s) or problem(s) addressed

The need for improved monitoring to inform water resource management (WRM) has been recognized, particularly in sub-Saharan Africa where networks are very limited. Burkina Faso is one country where the Government has developed an extensive long-term national network of gwl monitoring sites. However, the Department of Water Resources has recognized the limited application of the monitoring data and the potential to use the dataset to help develop tools to support WRM.

(c) Methodology or approach used

We calibrated lumped parameter models using long term gwl records from Burkina Faso, and used climate data to reconstruct gwls to as far as back 1902. The models were also driven with output from CMIP5 models to examine the range of potential gwl changes through the 21st Century.

(d) Results and conclusions derived from the project

Modelled groundwater hydrographs for the observed and reconstructed historic periods were categorized into three groups: (1) long term declines, likely due to anthropogenic influences; and, depending on the hydrogeological setting, either (2) short term intra-annual variability or (3) long-term multi-decadal variability. Group 3 shows a recovery in gwls following the 1970/80s drought. Gwl projections to the mid-century are relatively consistent in less arid regions; in more arid regions, most models show a rise in gwls but also a wide range of projections, from small decreases to very large increases. (e) Implications of the project relevant to selected conference theme, theory and/or practice

The intra-annual to multi-decadal variability present in the reconstructions has implications for WRM, and highlights the value of long term monitoring. Projections of gwls show that there can be consistency in the results of models in some regions of Burkina Faso, providing a basis for better informed WRM decisions. The approach developed is generic and applicable where long-term gwl data exist.

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