Groundwater recharge in Africa: identifying critical thresholds

开发地下水作为安全饮用水、灌溉和其他用途，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，地下水存在于非洲大部分地区，是一种比湖泊和河流中可用的水更大的资源。然而，一个关键的不确定因素是地下水开采的可持续性：地下水是否会得到补充，如果得到补充，补充的量是多少，未来会发生变化吗？这个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现有证据。研究小组将使用这些数据来寻找临界充电阈值的存在：超过这个阈值，充电可能不会发生或变得不可靠。他们将利用该数据集绘制非洲观测到的地下水补给量地图，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。与社会科学家一起，他们将利用研究结果来强调地下水补给可能成为可持续地下水开采的主要制约因素的地区和未来的情况，以及水井或钻孔可能干涸的地区和未来的情况，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以有许多不同的用途：它们应该有助于量化地下水开发的风险，并为了穷人的利益管理抽取方面的权衡；对于在非洲工作的水工程师来说，它们应该允许对地下水补给进行一次通过评估，以筛选补给是否可能成为一个项目的主要制约因素，并且还提供更准确地测量补给的工具；对于学术界来说，这些新的数据集可以用来验证全球或大陆尺度的陆地表面水文模型。一旦这项研究完成，由水援助组织召集的一个讲习班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。这项研究的结果将作为一个跳板，用来设计一个大型的跨学科实地研究方案，以检查导致这些临界补给阈值的过程，以便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.