Mapping irrigation potential from renewable groundwater in Africa - a quantitative hydrological approach
Mapping irrigation potential from renewable groundwater in Africa - a quantitative hydrological approach
复制标题
DOI：
10.5194/hess-19-1055-2015
复制
发表时间：
2015-01-01
影响因子：
6.3
通讯作者：
Villholth, K. G.
中科院分区：
文献类型：
--
作者：
Altchenko, Y.;Villholth, K. G.
地下水为非洲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 x 10(6) 公顷），而亚洲则为 14%。虽然亚洲许多地区地下水被过度开采用于灌溉，但之前的评估表明非洲部分地区的潜力尚未得到充分利用。与之前基于国家的估计相反，本文得出了整个大陆的分布式（0.5 度空间分辨率）地下水灌溉潜力图，以可再生地下水灌溉的农田比例表示。该方法以年度地下水平衡方法为基础，使用 41 年的水文数据，仅分配满足其他当前人类需求和环境要求后过量的地下水补给部分，同时忽略获取资源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，实施了三种情景，将30%、50%和70%的补给留给环境。采用分区方法中当前的主要作物和轮作以及相关的灌溉要求，以便将多余的补给转化为潜在的灌溉农田。结果显示，整个非洲大陆的地下水灌溉潜力分布不均匀，甚至在各个国家内部也是如此，主要反映了补给模式和耕地的存在与否。结果进一步表明，根据情景的不同，用于灌溉的年平均可再生地下水可用性范围为 692 至 1644 km(3)。可利用可再生地下水灌溉的农田总面积为 44.6 至 105.3 x 10(6) 公顷，相当于非洲大陆农田的 20.5 至 48.6%。特别是，半干旱的萨赫勒和东非地区存在巨大潜力，如果可持续和公平地发展，可以支持减贫。该地图是第一个评估，需要与其他因素的评估相补充，例如水文地质条件、地下水可利用性、土壤和社会经济因素以及更多的当地评估。
Groundwater provides an important buffer to climate variability in Africa. Yet, groundwater irrigation contributes only a relatively small share of cultivated land, approximately 1% (about 2 x 10(6) hectares) as compared to 14% in Asia. While groundwater is over-exploited for irrigation in many parts in Asia, previous assessments indicate an underutilized potential in parts of Africa. As opposed to previous country-based estimates, this paper derives a continent-wide, distributed (0.5 degrees spatial resolution) map of groundwater irrigation potential, indicated in terms of fractions of cropland potentially irrigable with renewable groundwater. The method builds on an annual groundwater balance approach using 41 years of hydrological data, allocating only that fraction of groundwater recharge that is in excess after satisfying other present human needs and environmental requirements, while disregarding socio-economic and physical constraints in access to the resource. Due to high 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 irrigation requirements in a zonal approach were applied in order to convert recharge excess to potential irrigated cropland. Results show an in homogeneously distributed groundwater irrigation potential across the continent, even within individual countries, mainly reflecting recharge patterns and presence or absence of cultivated cropland. Results further show that average annual renewable groundwater availability for irrigation ranges from 692 to 1644 km(3) depending on scenario. The total area of cropland irrigable with renewable groundwater ranges from 44.6 to 105.3 x 10(6) ha, corresponding to 20.5 to 48.6% of the cropland over the continent. In particular, significant potential exists in the semiarid Sahel and eastern African regions which could support poverty alleviation if developed sustainably and equitably. The map is a first assessment that needs to be complimented with assessment of other factors, e.g. hydrogeological conditions, groundwater accessibility, soils, and socio-economic factors as well as more local assessments.