Towards groundwater security in coastal East Africa

EA沿海地区的地下水资源处于危险之中。与沿海地区人口迅速增长有关的需求增加导致了不可持续和计划不周的钻井和开采。由于降雨的补给不足以支持抽取水的速度，因此经常发生海水侵入原淡水含水层的情况。在许多地区，供应家庭、工业和农业需求的威尔斯井已经变得太咸而不能使用，预计气候变化将加剧这一问题。印度洋区域海平面上升预计将导致沿着海水泛滥，而沿海地区主要是渗透性强的岩石，而降水模式的改变和温度的变化将影响通过渗透和补给补充含水层的水量。该地区的当地社区已经报告了潮汐和降雨模式的变化。水文和人口驱动因素的多样性使其成为一个非常具有挑战性的管理问题。 目前，EA地区沿海含水层的状况没有得到很好的控制，过去可能加剧问题的做法尚未明确确定。该项目将汇集来自肯尼亚、坦桑尼亚和科摩罗群岛的团队，以解决这一知识差距;合作并努力实现各自地区的水安全。将以各国沿海地区沿着选定地点为目标，采取综合办法，结合水文地质学家、水文学家和社会科学家的专门知识。将建立水文地质观测站，重点研究将确定沿海含水层的现状，并根据预测的人口和气候变化情景确定未来的威胁。将通过与最终用户和地方当局协商确定供水和监测需要，并寻求解决这些问题的最佳战略，第一步将是调查和收集关于每个试验地点现有威尔斯水井的安装、抽取、地下水梯度和盐度的所有现有数据。了解威尔斯井的位置、深度、抽取水量、流向和盐度，就可以对含水层的状况有一个总体了解。将调查和综合有关含水层的渗透率、孔隙度和蓄水率等水力特性的当地数据。将开展有针对性的电性地球物理调查，提供关于含水层结构和盐水分布的相关空间信息，还需要关于该系统水文驱动因素的数据，以了解每年有多少降雨渗入地下水以补充地下水储量（与人类使用的水量相比），以及降雨强度或频率的变化可能如何影响这一点。土地利用和土地利用变化也很重要;控制进入土壤和随后进入地下水的降雨量比例。回灌模型将是调查气候和土地利用变化的不同情景以及评估地下水脆弱性的重要工具。将把水的利用和开发的社会和政治方面纳入评估沿海淡水资源的可得性的演变与社会和水政治的演变之间的兼容性。研究人员将与每个地区的当地社区和利益攸关方团体合作，共同努力了解在供水可及性方面对社区影响最大的问题。研究人员和社区成员之间的双向知识交流对于努力为现有问题找到可行的解决办法和确保为今后人口和环境的变化做好准备至关重要。

Groundwater resources in the coastal zone of EA are at risk. Increased demand, linked to rapid population growth in the coastal margins, has led to unsustainable and ill-planned well drilling and abstraction. Sea water intrusion into formerly freshwater aquifers frequently occurs as recharge from rainfall is insufficient to support the rate at which water is extracted. Wells supplying domestic, industrial and agricultural needs have, in many areas, become too saline for use.Climate change is expected to exacerbate this problem. Rising sea levels in the Indian Ocean region are projected to cause inundation of saltwater along the coastal zone, which is dominated by highly-permeable rock, while altered precipitation patterns and temperature change will affect the amount of water replenishing the aquifer through infiltration and recharge. Local communities across the region are already reporting changing tidal and rainfall patterns. The multiplicity of hydrological and demographic driving factors makes this a very challenging issue for management. At present the state of coastal aquifers in the EA region is not well constrained and past practices which may have exacerbated the problem have not been clearly identified. This project will bring together teams from Kenya, Tanzania and the Comoros Islands to address this knowledge gap; collaborating and working towards achieving water security in their respective areas. An integrative approach, combining the expertise of hydrogeologists, hydrologists and social scientists, will target selected sites along the coastal zone in each country. Hydrogeologic observatories will be developed where focussed research will identify the current condition of the coastal aquifers and identify future threats based on projected demographic and climate change scenarios. Water supply and monitoring needs will be identified through consultations with end-users and local authorities and optimum strategies for addressing these sought.An initial step will be to survey and bring together all existing data on well installations, abstraction, groundwater gradients and the salinity of existing wells at each pilot site. Understanding where wells are located, how deep they are, how much water is abstracted, what the flow directions are and what the salinity is, provides an overview of the state of the aquifer. Local data on hydraulic properties, such as the permeability, porosity, and storativity of the aquifer will be investigated and synthesised. Targeted electrical geophysical surveys, which provide relevant spatial information on both the aquifer structure and the saltwater distribution, will be undertaken.Similarly data is needed on the hydrological drivers in the system; to understand how much of annual rainfall infiltrates to replenish groundwater reserves (compared to the amount abstracted for human use) and how this might be impacted by changes in rainfall intensity or frequency. Land use and land use change is also important; controlling the proportion of incident rainfall which reaches the soil and subsequently groundwater. Recharge modelling will be an important tool for investigating different scenarios for climate and land use change and evaluating groundwater vulnerability. The social and political aspects of water use and development will be incorporated to assess the compatibility between the evolution of the availability of coastal freshwater resources and those of society and water politics. Researchers will engage with local community and stakeholder groups in each area and work together towards understanding the issues most affecting the communities with regards accessibility to water supply. A two-way exchange of knowledge between researchers and community members is essential in working towards feasible solutions to existing problems and ensuring preparedness for the changes in demographics and environment in the future.