Mapping groundwater recharge in Africa from ground observations and implications for water security
Mapping groundwater recharge in Africa from ground observations and implications for water security
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DOI：
10.1088/1748-9326/abd661
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发表时间：
2021-02
影响因子：
6.7
通讯作者：
A. MacDonald;R. Lark;R. Taylor;T. Abiye;H. Fallas;G. Favreau;I. Goni;S. Kebede;B. Scanlon;J. Sorensen;M. Tijani;K. Upton;C. West
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作者：
A. MacDonald;R. Lark;R. Taylor;T. Abiye;H. Fallas;G. Favreau;I. Goni;S. Kebede;B. Scanlon;J. Sorensen;M. Tijani;K. Upton;C. West
地下水是非洲大部分地区供水的基础，随着对安全用水需求的增加，地下水的开发也在增加。补给率是评估地下水开发潜力的一个关键组成部分，但除全球模型外，尚未绘制整个非洲的地图。在这里，我们量化了1970-2019年期间非洲各地的长期平均（LTA）分布式地下水补给率，这些地下水补给率来自134个基于地面的估计值，并在统计上进行了放大。自然扩散和局部集中补给，在这种机制是广泛的，包括但不包括离散泄漏从大河，湖泊或灌溉。我们发现，可测量的LTA补给被发现在大多数环境中的平均年代际补给深度在干旱和半干旱地区分别为60毫米（30-140毫米）和200毫米（90-430毫米）。线性混合模型表明，在非洲大陆的规模上，只有LTA降雨量与LTA补给相关-纳入其他气候和陆地因素并不能改善模型。克立格法表明空间依赖性900公里，表明其他因素比LTA降雨是重要的，在当地尺度。我们估计，非洲的平均十年补给量为15000 km 3（4900- 45000 km 3），约占整个非洲大陆估计地下水储量的2%，但其特点是北非高储存/低补给沉积含水层和非洲热带大部分地区低储存/高补给风化结晶岩含水层之间存在明显的变化。这种分布大大加强了非洲的水安全，因为许多补给量低的国家拥有大量地下水储存，而储存量低的国家则有大量定期补给。该数据集提供了非洲地下水储存可再生性的第一个基于地面的近似值，可用于完善和验证全球和大陆水文模型，同时还提供了应对未来变化的基线。
Groundwater forms the basis of water supplies across much of Africa and its development is rising as demand for secure water increases. Recharge rates are a key component for assessing groundwater development potential, but have not been mapped across Africa, other than from global models. Here we quantify long-term average (LTA) distributed groundwater recharge rates across Africa for the period 1970–2019 from 134 ground-based estimates and upscaled statistically. Natural diffuse and local focussed recharge, where this mechanism is widespread, are included but discrete leakage from large rivers, lakes or from irrigation are excluded. We find that measurable LTA recharge is found in most environments with average decadal recharge depths in arid and semi-arid areas of 60 mm (30–140 mm) and 200 mm (90–430 mm) respectively. A linear mixed model shows that at the scale of the African continent only LTA rainfall is related to LTA recharge—the inclusion of other climate and terrestrial factors do not improve the model. Kriging methods indicate spatial dependency to 900 km suggesting that factors other than LTA rainfall are important at local scales. We estimate that average decadal recharge in Africa is 15 000 km3 (4900–45 000 km3), approximately 2% of estimated groundwater storage across the continent, but is characterised by stark variability between high-storage/low-recharge sedimentary aquifers in North Africa, and low-storage/high-recharge weathered crystalline-rock aquifers across much of tropical Africa. African water security is greatly enhanced by this distribution, as many countries with low recharge possess substantial groundwater storage, whereas countries with low storage experience high, regular recharge. The dataset provides a first, ground-based approximation of the renewability of groundwater storage in Africa and can be used to refine and validate global and continental hydrological models while also providing a baseline against future change.