Long-term increase in diffuse groundwater recharge following expansion of rainfed cultivation in the Sahel, West Africa

Ibrahim, Maïmouna; Favreau, Guillaume; Scanlon, Bridget R.; Seidel, Jean Luc; Le Coz, Mathieu; Demarty, Jérôme; Cappelaere, Bernard

Long-term increase in diffuse groundwater recharge following expansion of rainfed cultivation in the Sahel, West Africa | Augmentation sur le long terme de la recharge diffuse des aquifères suite à l’expension des cultures pluviales dans le Sahel, Afrique de l’Ouest Incremento a largo plazo en la recarga difusa de agua subterránea siguiendo la expansión de cultivos de secano en el Sahel, África Occidental 西非Sahel地区靠雨水灌溉的耕种面积扩大之后地下水弥散补给长期增加 Aumento da recarga difusa de águas subterrâneas a longo prazo após a expansão das culturas regadas a partir da precipitação no Sahel, África Ocidental

2014

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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