Groundwater contamination, recharge, and flow dynamics in the anthropogenic environment

Abstract

Understanding the dynamics of groundwater resources subject to the pressures of human activity has become a central topic in 21st century hydrogeology. Groundwater availability is defined both in terms of quantity – how much water is stored an aquifer – and in terms of quality – how much groundwater of sufficient quality is available for consumption. Changes in land use have directly impacted both of these facets. Due to its hidden nature, accurately determining the amount of available groundwater is notoriously difficult, and the added complexity of human stressors only augment these difficulties. In addition, the human landscape itself is undergoing rapid change, with a consistent increase in the human population, most of who now live in cities. This population increase has led to increasing land surface dedicated to anthropogenic use, and requires ever greater amounts of water resources for drinking water, agricultural applications, and industrial processes. Hence why a rising number of efforts have emerged in scientific literature on the topic of groundwater in the human environment. With these facts in mind, this thesis has dealt with identifying the impacts of various anthropogenic land-use patterns on groundwater resources, and the specific discussions around these impacts in modern studies. With the knowledge assembled from current literature, we explored the applicability of both established and novel hydrological and hydrogeological tools to accurately characterize the groundwater cycle in the anthropogenic environment. Our study was carried out at a test site in an urbanizing catchment on the Swiss Plateau, containing a shallow, unconfined fluvioglacial aquifer. Emphasis was therefore placed on an urban area where the groundwater is actively exploited for municipal and agricultural water supply. Our methods included an analytical water balance to estimate groundwater recharge using readily-available public data, followed by statistical analysis of chemical indicators to identify the sources and pathways of water into and out of an aquifer. With minimal public data, we were able to estimate historical patterns of groundwater recharge over the course of a decade, including an assessment of changes in the individual variables of the groundwater balance – notably storm runoff versus infiltration. To supplement public data for further analysis, a network of groundwater monitoring wells was installed across the most urbanized area of our study catchment, from which a database including physical, chemical, and isotopic variables was constructed. For chemical analyses, inorganic ions, with a long record of use, were analyzed along with organic micropollutants, which are a relatively novel tool specific to human environments. This data, combined with information on the layout of the river network and the sewer system, allowed us to evaluate potential interactions between groundwater, surface water, and the sewer network. These results have demonstrated the suitability of our approach to capture groundwater dynamics in an urbanizing catchment.