Groundwater recharge in Africa: identifying critical thresholds

用于安全饮用水、灌溉和其他用途的地下水的开发为改善许多非洲人民的生活提供了巨大的潜力。最近的研究表明，非洲大部分地区都有地下水，这是一种比湖泊和河流中可用的水更多的资源。然而，一个关键的不确定性是，抽取地下水的可持续性将有多强：它是否得到了补给？如果是的话，补给幅度有多大？未来这种变化会有多大？这一研究项目将汇集一个由非洲、欧洲和美国科学家组成的团队，研究非洲各地地下水补给的所有可用证据。该团队将使用这些数据来搜索关键充电阈值的存在：超过该阈值的充电可能不会发生或变得不可靠。他们将使用数据集为非洲绘制一张观测到的地球定时器补给量地图，并寻找整个非洲大陆的系统性变化。该小组还将利用这个机会研究测量地下水补给的不同方法，并确定最适合非洲条件的方法。他们将与社会科学家一起，利用研究结果来突出地下水补给可能成为可持续地下水提取的主要制约因素的地区和未来情景，以及水井或钻孔可能干涸的地区，特别是对农村贫困人口的影响。地下水补给图和临界阈值的量化可有许多不同的用途：它们应有助于量化地下水开发的风险，并在抽象的基础上进行权衡取舍，以造福穷人；对于在非洲工作的水利工程师来说，他们应能够对地下水补给进行首次全面评估，以筛选补给是否可能成为项目的主要制约因素，并为更准确地衡量补给提供工具；对学术界来说，这些新的数据集可用于验证全球或大陆尺度的陆面水文模型。一旦研究完成，水援助组织召开的研讨会和网络研讨会将有助于探索研究结果对规划和实施非洲新的水项目的影响。这项研究的结果将被用作设计一个大型跨学科研究实地方案的跳板，以审查导致这些关键补给阈值的过程，以便能够更可靠地预测未来地下水开发可能变得不可持续的地方，并探索如何在这些关键地区最好地管理地下水。

The development of groundwater for safe drinking water, irrigation and other uses offers huge potential for improving the lives of many African people. Recent research showed that groundwater was present in most parts of Africa and represented a resource greater than the water available in lakes and rivers. However, a key uncertainty is how sustainable groundwater abstraction will be: is it being replenished and if so by how much and will this change in the future?This research project will bring together a team of African, European and US scientists to examine all the available evidence for groundwater recharge across Africa. The team will use these data to search for the existence of critical recharge thresholds: conditions beyond which recharge may not occur or become unreliable. They will use the datset to develop a map of observed groundater recharge volumes for Africa and look for systematic changes across the continent. The team will also use the opportunity to examine the different methods for measuring groundwater recharge and identify the most appropriate for African conditions.Together with social scientists they will use the results of the research to highlight areas and future scenarios where groundwater recharge may become a major contraint on sustainable groundwater abstraction, and where wells or boreholes may run dry, impacting particularly on the rural poor. The maps of groundwater recharge, and the quantification of critical thresholds can have many different uses: they should help quantify the risks of groundwater development and manage tradeoffs in abstraction for the benefit of the poor; for water engineers working in Africa, they should allow a first pass assessment of groundwater recharge to screen whether recharge may be a major constraint on a project, and also provide the tools for measuring recharge more accurately; for the academic community these new datasets can be used to validate global or continetal scale land surface hydrological models. Once the research is completed a workshop and webinar convened by WaterAid will help explore the implications of the research results for planning and implementing new water projects in Africa.The results of this research will be used as a springboard to design a large field programme of interdisciplinary research to examine the processes which lead to these critical recharge thresholds to allow much more reliable forecasts of where groundwater development may become unsustainable in the future and to explore how groundwater can be best managed in these critical areas.