Ouedraogo, Issoufou
[Ecole Supérieure d'Ingénieurs, Université de Fada N'Gourma, Burkina Faso]
Vanclooster, Marnik
[UCL]
Groundwater is a major component of available freshwater and it is an essential natural resource for overall development. In the hydrological system, groundwater is closely linked to surface water. Groundwater and surface water should, therefore, be managed coherently together in an integrated way. However, there are some inherent structural challenges related to such an approach. First, the areal extent of surface water basins and the underlying groundwater systems often differ radically (BGR and UNESCO, 2012), making groundwater management by river basin organizations complex. Second, given the subsurface nature of groundwater, data on groundwater status is often scarce and of poor quality, in particular in many parts of the developing world like in Africa. There is, therefore, a need to improve the capacity of monitoring groundwater bodies as a support for integrated water management of large river basins. We address this significant knowledge gap for groundwater pollution in Africa methods for assessing groundwater pollution risk at the African scale. To do so, we compile the most recent continental-scale information on soil, land use, geology, hydrogeology and climate in a Geographical Information System at the resolution of 15 kmx15 km and the 1:60,000,000 scale. We produced a vulnerability map by using the generic DRASTIC vulnerability indicator (Ouedraogo et al., 2016). This map revealed that groundwater is highly vulnerable in Central and West Africa groundwater basins, where the water table is very low. In addition, very low vulnerability classes are found in the large sedimentary basins of Africa deserts where groundwater is situated in very deep aquifers. The generic groundwater pollution risk map is obtained by overlaying the DRASTIC vulnerability indicator with current land use. The northern, central and western parts of the African continent are dominated by high vulnerability classes and very strongly related to water table depths and development of agricultural activities. The generic methods based on the DRASTIC model are further refined using statistical models. With these approaches, monitoring data are integrated into the vulnerability mapping. Given the availability of data, we concentrate first on nitrate vulnerability mapping. To this end, groundwater nitrate contamination data are compiled (Ouedraogo and Vanclooster, 2016) and used to calibrate as well linear and nonlinear statistical models (Ouedraogo et al.2018); the latter performing much better as compared to simple linear statistical models. This study will help to raise awareness of the manager's International Basin Authorities or Transboundary Basin Organizations in Africa and in particular on transboundary groundwater pollution issues.
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Bibliographic reference |
Ouedraogo, Issoufou ; Vanclooster, Marnik. Challenges in groundwater pollution management in transboundary basins: Groundwater pollution mapping at the African scale.Workshop "Expert Consultation for the Volta Basin Use Case" (East Legon, Accra, Ghana, du 22/02/2020 au 27/02/2020). |
Permanent URL |
http://hdl.handle.net/2078.1/227857 |