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Long-term increase in diffuse groundwater recharge following expansion of rainfed cultivation in the Sahel,West Africa |
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| Authors: | Maïmouna Ibrahim Guillaume Favreau Bridget R Scanlon Jean Luc Seidel Mathieu Le Coz Jérôme Demarty Bernard Cappelaere |
| Institution: | 1. UMR 5569 HSM, Pl. E. Bataillon, cc. MSE, Université Montpellier 2 (UM2), 34095, Montpellier cedex 5, France 2. Faculté des Sciences, Département de Géologie, Université Abdou Moumouni de Niamey, BP 10662, Niamey, Niger 3. UMR 5569 HSM, Pl. E. Bataillon, cc. MSE, Institut de Recherche pour le Développement (IRD), 34095, Montpellier cedex 5, France 4. Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, 78713, USA 5. UMR 5569 HSM, Place E. Bataillon, CC MSE, Centre National de la Recherche Scientifique (CNRS), 34095, Montpellier, France 6. IC2MP/Hydrasa, Université de Poitiers, rue Michel Brunet, 86022, Poitiers, France |
| Abstract: | Rapid population growth in sub-Saharan West Africa and related cropland expansion were shown in some places to have increased focused recharge through ponds, raising the water table. To estimate changes in diffuse recharge, the water content and matric potential were monitored during 2009 and 2010, and modeling was performed using the Hydrus-1D code for two field sites in southwest Niger: (1) fallow land and (2) rainfed millet cropland. Monitoring results of the upper 10 m showed increased water content and matric potential to greater depth under rainfed cropland (>2.5 m) than under fallow land (≤1.0 m). Model simulations indicate that conversion from fallow land to rainfed cropland (1) increases vadose-zone water storage and (2) should increase drainage flux (～25 mm year?1) at 10-m depth after a 30–60 year lag. Therefore, observed regional increases in groundwater storage may increasingly result from diffuse recharge, which could compensate, at least in part, groundwater withdrawal due to observed expansion in irrigated surfaces; and hence, contribute to mitigate food crises in the Sahel. |
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