Groundwater provides an important buffer to climate variability in Africa.Yet, groundwater irrigation contributes only a relatively small share ofcultivated land, approximately 1% (about 2 × 106 hectares)as compared to 14% in Asia. While groundwater is over-exploited forirrigation in many parts in Asia, previous assessments indicate anunderutilized potential in parts of Africa. As opposed to previouscountry-based estimates, this paper derives a continent-wide, distributed(0.5° spatial resolution) map of groundwater irrigation potential,indicated in terms of fractions of cropland potentially irrigable withrenewable groundwater. The method builds on an annual groundwater balanceapproach using 41 years of hydrological data, allocating only that fractionof groundwater recharge that is in excess after satisfying other presenthuman needs and environmental requirements, while disregardingsocio-economic and physical constraints in access to the resource. Due tohigh uncertainty of groundwater environmental needs, three scenarios,leaving 30, 50 and 70% of recharge for the environment, were implemented.Current dominating crops and cropping rotations and associated irrigationrequirements in a zonal approach were applied in order to convert rechargeexcess to potential irrigated cropland. Results show an inhomogeneouslydistributed groundwater irrigation potential across the continent, evenwithin individual countries, mainly reflecting recharge patterns andpresence or absence of cultivated cropland. Results further show thataverage annual renewable groundwater availability for irrigation ranges from 692 to1644 km3 depending on scenario. The total area of cropland irrigablewith renewable groundwater ranges from 44.6 to 105.3 × 106 ha,corresponding to 20.5 to 48.6% of the cropland over the continent. Inparticular, significant potential exists in the semi-arid Sahel and easternAfrican regions which could support poverty alleviation if developedsustainably and equitably. The map is a first assessment that needs to be complimentedwith assessment of other factors, e.g. hydrogeological conditions,groundwater accessibility, soils, and socio-economic factors as well as morelocal assessments.
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机译：地下水为非洲的气候变化提供了重要的缓冲。然而，地下水灌溉仅占耕地的一小部分，约为1％（约2×10 6 公顷），而亚洲为14％。尽管亚洲许多地方的地下水被过度开发用于灌溉，但先前的评估表明非洲部分地区的地下水利用潜力不足。与以前的基于国家的估计相反，本文得出了一张遍布整个非洲大陆的，具有一定分布潜力（0.5°空间分辨率）的地下水灌溉潜力图，以可灌溉的地下水中可灌溉的农田所占比例表示。该方法建立在使用41年水文数据的年度地下水平衡方法的基础上，在满足其他当前人类需求和环境要求之后，仅分配过量的地下水补给量，而忽略了对资源获取的社会经济和物理限制。由于地下水环境需求的高度不确定性，实施了三种方案，分别为环境留出了30％，50％和70％的补给量。采用当前主要农作物和轮作以及分区灌溉的相关灌溉要求，以将补给量过量转化为潜在灌溉量农田。结果表明，即使在单个国家内部，整个非洲大陆的地下水灌溉潜力也不均匀，主要反映了补给模式和耕地的存在与否。结果进一步表明，取决于情景，灌溉的年平均可再生地下水可用量在692至1644 km 3 之间。可再生地下水灌溉的农田总面积为44.6至105.3×10 6 公顷，相当于该大陆耕地的20.5至48.6％。特别是，在半干旱的萨赫勒地区和非洲东部地区，如果可持续地和公平地发展，则有可能支持扶贫。该地图是首次评估，需要与其他因素（例如，水文地质条件，地下水可及性，土壤和社会经济因素以及更多本地评估。
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