Towards groundwater security in coastal East Africa

EA沿海地区的地下水资源面临风险。需求的增加与沿海地区人口的快速增长有关，导致了不可持续和计划不周的油井钻探和开采。海水侵入以前的淡水含水层的情况经常发生，因为降雨的补给不足以支持取水的速度。在许多地区，供应家庭、工业和农业需求的水井已经变得太咸而无法使用。气候变化预计将加剧这一问题。印度洋地区海平面上升预计将导致沿海地区海水泛滥，沿海地区以高渗透性岩石为主，而降水模式和温度变化将影响通过渗透和补给补给含水层的水量。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得这对管理来说是一个非常具有挑战性的问题。目前，东亚地区沿海含水层的状况没有得到很好的约束，过去可能加剧这一问题的做法也没有得到明确的确认。该项目将汇集肯尼亚、坦桑尼亚和科摩罗群岛的小组，以解决这一知识差距；在各自地区合作和努力实现水安全。综合办法结合了水文地质学家、水文学家和社会科学家的专业知识，将针对每个国家沿海地带选定的地点。将建立水文地质观测站，其中重点研究将查明沿海含水层的现状，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的协商以及解决这些问题的最佳战略来确定供水和监测需求。第一步将是调查和汇集关于每个试验点的水井安装、抽水、地下水梯度和现有水井盐度的所有现有数据。了解水井的位置、深度、抽取了多少水、流向是什么以及盐度是什么，可以提供对含水层状况的概述。将对当地有关水力特性的数据进行调查和综合，如含水层的渗透率、孔隙度和储水量。将进行有针对性的电子地球物理调查，提供有关含水层结构和咸水分布的相关空间信息。同样需要关于系统中水文驱动因素的数据；了解每年有多少降雨渗入以补充地下水储量(与供人类使用的抽水量相比)，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的变化也很重要；控制进入土壤并随后进入地下水的降雨的比例。补给模型将是调查气候和土地利用变化的不同情景和评估地下水脆弱性的重要工具。将纳入用水和发展的社会和政治方面，以评估沿海淡水资源可获得性的演变与社会和水政治之间的兼容性。研究人员将与每个地区的当地社区和利益攸关方团体接触，共同努力了解在供水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并确保为未来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.