International: Use of phase-sensitive radar to monitor discharge and recharge of Moroccan aquifers

这项拟议研究的动机是，在缺乏关于含水层充水程度的良好信息的情况下，管理取水的困难，撒哈拉以南非洲和西非干旱和半干旱地区地下水补给将减少的日益普遍的共识，以及日益增加的抽取对含水层的压力。拟议工作的目的是确定使用国家环境研究中心开发的仪器(APRES)帮助干旱和半干旱地区管理水资源的可行性，方法是允许在不借助钻孔的情况下监测地下水位深度。这一挑战既有技术方面的，也有社会方面的。自主相敏无线电回波探测仪(APRES)是由英国南极调查局和伦敦大学学院联合开发的，目的是监测南极冰盖浮动部分的厚度变化。重量轻、坚固耐用且相对便宜的APRE设计用于在冰盖上部署一年或更长时间，以承受南极冬季的严酷条件。检测冰盖底部变化深度的问题基本上与在其他干燥环境中检测地下水位深度的问题相同。因此，APRE有可能被用作相对便宜的(与钻孔相比)监测地下水位深度的方法，为协助管理抽水提供了工具。我们选择摩洛哥进行这项研究。摩洛哥拥有各种有用的土壤类型、气候条件和地下水位深度。它的许多井眼提供了必要的地面真相，提供了一种对地下水位深度的独立测量。2017年3月，摩洛哥进行了一项简短的试点研究，由NERC官方发展援助创新泵--优质赠款提供资金，并由本提案的合作伙伴在当地提供便利。结果令人振奋。访问了几个地点，地下水位深度各不相同，主要是为了找到一个适合数小时部署的地点。该仪器能够检测大多数地点的地下水位，并能够在6小时(夜间)试验中监测其变化的深度。试点取得的良好结果现在促使下一步--在摩洛哥与我们的摩洛哥合作伙伴一起进行一项全面的研究，以更准确地确定仪器的能力范围，并减少使用该仪器监测地下水深度的障碍：易用性、坚固性和成本。在拟议的研究中，对摩洛哥不同的实地考察将使人们能够对一系列土壤类型、土壤水分含量、地下水位深度、当地条件(城市/农村)和季节(湿/干)的使用情况进行评估。仪器和天线将被仔细检查，以确定哪里可以降低成本，以及需要进行哪些加固来处理非极性条件。最后，数据处理步骤将被合理化，这样非专家就可以执行它们。这一挑战的社会方面，如何确保采用任何新技术，将通过两种方式解决。我们发起的一项独立但平行的研究(将由发展第一小组于2017年10月和11月进行)将调查如何利用能够实时监测含水层排放和补给的能力来提高缺水地区地下水开采的可持续性。其次，我们在摩洛哥的项目合作伙伴将准备一份实施路径文件，以确定如何在摩洛哥推广这项技术。如果我们在这里提出的项目确认了在干旱地区使用APRES监测地下水的技术可行性，i-Teams研究的结果和实施路径报告将使我们处于有利地位，推动该项目在摩洛哥内外的下一个应用水平。

The motivation for the proposed study is the difficulty in managing water abstraction in the absence of good information about the degree of charge of aquifers, the growing consensus that groundwater recharge will diminish in arid and semiarid areas in sub-Saharan and western Africa, and the ever-increasing pressure on aquifers from increased abstraction.The aim of the proposed work is to determine the feasibility of using a NERC-developed instrument (ApRES) to aid the management of water resources in arid and semi-arid regions by allowing water-table depths to be monitored without recourse to boreholes. The challenge has both technical and societal aspects.The Autonomous phase-sensitive Radio Echo Sounder (ApRES) was jointly developed by the British Antarctic Survey and University College London to monitor the changing thickness of the floating portion of the Antarctic Ice Sheet. Lightweight, robust and relatively inexpensive, ApRES was designed to be deployed on an ice sheet for a year or more, withstanding the harsh conditions of the Antarctic winter.The problem of detecting the changing depth of the base of an ice sheet is essentially the same as that of detecting the depth of the water table in an otherwise dry environment. ApRES can therefore potentially be used as relatively inexpensive (compared with boreholes) method for monitoring the depth of the water table, providing a tool to assist in the management of water abstraction.Our choice of country for this study is Morocco. Morocco boasts a useful range of soil types, climatic conditions, and water table depths. Its many boreholes provide the necessary ground truth by offering an independent measure of the depth of the water table.A short pilot study was undertaken in Morocco in March 2017, funded through a NERC ODA Innovation pump-prime grant, and locally facilitated by the partners on the present proposal. The results were promising. Several sites were visited, with varying water table depths, primarily to find a suitable location for a multi-hour deployment. The instrument was able to detect the water table at most of the sites and was able to monitor its changing depth over a 6-hour (overnight) trial.The promising results from the pilot now prompts the next step - a comprehensive study in Morocco, alongside our Moroccan partners, to determine more precisely the envelope of capability of the instrument, and to reduce impediments to its use in monitoring groundwater depth: ease of use, robustness, cost. In the proposed study visits to different field sites in Morocco will allow the utility of ApRES to be assessed for a range of soil types, soil moisture contents, water table depths, local conditions (urban/rural) and seasons (wet/dry). The instrument and antennas will be scrutinised to see where costs can be reduced and what hardening will be needed to deal with the non-polar conditions. Finally, the data-processing steps will be rationalised such that a non-expert could carry them out.The societal aspect of the challenge, how to ensure uptake of any new technique, will be addressed in two ways. An independently resourced, but parallel study that we have instigated (to be delivered by Development i-Teams in October and November 2017) will investigate how having the ability to monitor the discharge and recharge of aquifers in real time can be used to improve the sustainability of groundwater exploitation in water-scarce regions. Second, our project partners in Morocco will prepare an implementation pathways document to define how the technology could be rolled out in Morocco. Should the project that we are proposing here confirm the technical feasibility of using ApRES for ground water monitoring in arid regions, the outcomes of the i-Teams study and the implementation pathways report will put us in a strong position to take the project forward to the next level of application, both within Morocco and beyond.