Advances in thermal tracers for measuring and managing groundwater resources

全球地下水资源正在枯竭，这引发了人们对未来水和粮食安全的担忧。由于气候变化以及人口重新分布和城市环境中地下水需求的增加，目前的情况预计在未来几十年将进一步恶化。不可持续的地下水开采通常被认为仅限于第三世界国家，但加拿大境内的地区最近因干旱而经历了地下水短缺。全面的地下水管理必须同时考虑社会和生态系统的地下水需求，因为向河流排放地下水对于调节温度和维持旱季的水流至关重要。由于难以测量进出含水层的地下水流量(单位面积流量)，可持续的地下水管理往往具有挑战性。使用示踪剂估计这些通量的标准方法通常只适用于某些环境，需要昂贵的采样和分析，并且具有假设和不确定性的特点。因此，迫切需要发展改进的方法，以廉价和准确地追踪地下水通量。*由于水流诱导热平流并扰乱地下温度，可以利用热量来研究地下水的运动。与其他地下水示踪剂相比，热量具有优势，因为它始终存在于地下，持续监测成本低廉，而且不需要进一步的实验室分析。水资源管理界对利用热量作为地下水示踪剂的现有分析技术的吸收一直受到限制，因为大多数常用方法限于深度不到一米。这项研究计划的总体目标是开发新的综合技术和技术，根据深层和浅层含水层的温度追踪地下水，以便为满足社会和生态系统需求的地下水资源的可持续管理提供信息。这项研究计划将培训七名学生，将包括仪器设计、数据收集和模型开发。侧重于浅层环境的研究将提供监测含水层-河流交换的改进方法，以帮助河流恢复和栖息地保护，特别是在加拿大东南部，由于河流变暖，那里的鲑鱼数量正在下降，那里的地下水对创造鱼类栖息地至关重要。侧重于热量示踪以量化进出深层含水层的流量的研究将为地下水工程师提供新的工具，以监测地下水补给的长期变化或评估在新地点开发井田的可行性。在这个研究项目中开发的知识将通过期刊出版物、演讲和短期课程传递给其他学者和更广泛的水资源管理界。

Global groundwater resources are being depleted, which is eliciting concern over future water and food security. The present situation is expected to be exacerbated in the coming decades due to climate change as well as population redistribution and increased groundwater demand in urban environments. Unsustainable groundwater extraction is often thought to be limited to third world countries, but regions within Canada have recently experienced groundwater shortages due to droughts. Holistic groundwater management must consider both societal and ecosystem groundwater demands because groundwater discharge to rivers is critical for modulating temperatures and sustaining flows during the dry season. Sustainable groundwater management is often challenging due to difficulties associated with measuring groundwater fluxes (flow per unit area) to and from aquifers. Standard approaches to estimate these fluxes using tracers are typically only applicable in certain environments, require expensive sampling and analyses, and are characterized by assumptions and uncertainties. Thus, there is a critical need to develop improved methods to inexpensively and accurately trace groundwater fluxes.******Heat can be used to study groundwater movement because water flow induces heat advection and disturbs subsurface temperatures. Heat offers advantages over other groundwater tracers as it is always present in the subsurface, it is inexpensive to continuously monitor, and it does not require further laboratory analysis. Uptake of existing analytical techniques for using heat as a groundwater tracer has been limited in the water resources management community because most common methods are restricted to depths less than one meter. The overall objective of this research program is to develop new integrated technology and techniques for tracing groundwater from temperature in deep and shallow aquifers to inform the sustainable management of groundwater resources for both societal and ecosystem needs. This research program, which will train seven students, will include instrument design, data collection, and model development. Research focused on shallow environments will provide improved methods for monitoring aquifer-river exchanges to aid in river restoration and habitat conservation, particularly in southeastern Canada where salmon populations are in decline due to river warming and where groundwater is critical for creating fish habitat. Research focused on heat tracing to quantify flows to and from deeper aquifers will provide new tools for groundwater engineers to monitor long-term changes in groundwater recharge or assess the viability of developing well fields in new locations. Knowledge developed in this research program will be transferred to other academics as well as the broader water resources management community via journal publications, presentations, and short courses.********