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

提出这项研究的动机是，在缺乏有关含水层充注程度的良好信息的情况下，管理抽水是困难的，人们越来越一致地认为，在撒哈拉以南和西非的干旱和半干旱地区，地下水补给将减少，以及抽水增加对含水层的压力不断增加。拟议的工作的目的是确定是否有可能使用非洲经委会开发的仪器（ApRES）来协助干旱和半干旱地区的水资源管理，方法是不借助钻孔就能监测地下水位深度。这一挑战既有技术方面的，也有社会方面的。自主相敏无线电回声测深仪（ApRES）是由英国南极调查局和伦敦大学学院联合开发的，用于监测南极冰盖漂浮部分厚度的变化。ApRES重量轻，坚固耐用，价格相对便宜，设计用于在冰盖上部署一年或更长时间，可以承受南极冬季的恶劣条件。探测冰盖底部深度变化的问题本质上与探测其他干燥环境中的地下水位深度的问题是一样的。因此，ApRES有可能作为监测地下水位深度的相对便宜的方法（与钻孔相比），提供一种协助管理抽取水的工具。我们选择的国家是摩洛哥。摩洛哥拥有一系列有用的土壤类型、气候条件和地下水位。它的许多钻孔通过提供对地下水位深度的独立测量，提供了必要的地面真相。2017年3月，在摩洛哥进行了一项短期试点研究，由NERC官方发展援助创新项目资助，并由本提案的合作伙伴在当地提供便利。结果很有希望。研究人员走访了几个地下水位不同的地点，主要是为了找到适合部署数小时的地点。该仪器能够探测到大多数地点的地下水位，并能够在6小时（一夜）的试验中监测其深度变化。试点项目取得的令人鼓舞的结果现在促使我们采取下一步行动——与我们的摩洛哥合作伙伴一起在摩洛哥进行一项全面研究，以更精确地确定该仪器的能力范围，并减少其在监测地下水深度方面的障碍：易用性、可靠性和成本。在拟议的研究中，对摩洛哥不同实地地点的访问将允许评估ApRES的用途，包括一系列土壤类型、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）。仪器和天线将被仔细检查，以确定哪些地方可以降低成本，以及需要进行哪些硬化来应对非极性条件。最后，数据处理步骤将合理化，使非专家也能执行。这一挑战的社会方面，即如何确保任何新技术的采用，将通过两种方式解决。我们发起了一项独立的并行研究（将由Development i-Teams于2017年10月和11月交付），该研究将调查如何利用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该技术。如果我们在这里提出的项目证实了在干旱地区使用ApRES进行地下水监测的技术可行性，那么i-Teams研究的结果和实施路径报告将使我们处于有利地位，将该项目推进到摩洛哥内外的下一个应用阶段。

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.