Situation and stresses: a spatial analysis of near-surface drinking water resources in Germany

Decreasing groundwater recharge and competing water uses challenge drinking water supplies worldwide and noticeably in Germany as well. Groundwater is a significant source of drinking water, making it essential to maintain its quality and quantity. In Germany, about 74% of drinking water originates from groundwater. However, various stress factors significantly affect the quality and quantity of the groundwater resource. The combined effects of climate change and diverse physical and social factors pose a central challenge for current and future drinking water supply. To address this challenge, a good understanding of the varieties of situations needs to support tools and decision-making frameworks to manage groundwater sustainably and ensure resilient drinking water. This study conducts a nationwide spatial analysis of various influencing factors. It focuses primarily on drinking water protection areas used for agriculture, examining their natural and hydro-climatic characteristics and changes, and the nitrate pollution they experience due to agricultural activities. Currently, Germany has around 11270 designated drinking water protection areas, of which 84 % are used for agriculture. We create a unique dataset for them. This spatial dataset quantifies numerous potential characteristics and stress factors for each of the (n) drinking water protection areas. These factors include groundwater recharge rates, drought response times, agricultural usage, nitrate pollution, aquifer type, and more. Applying clustering methods to the n x m matrix data helps to identify typical situations for drinking water supply. By considering three dimensions—drinking water extraction/hydrogeology, nitrate pollution, and drought vulnerability we aim to characterize and depict diverse situations across Germany while determining broader trends. Achieving sustainable drinking water management requires a systematic analysis of the heterogeneous natural, political-regulatory, and agro-economic conditions to identify transferable success factors. Building on this study with model developments in the "LURCH-StressRes" project, we later aim to develop transferable stress tests for the identified typical situations across Germany to inform adaptation and best practices for achieving sustainable nationwide drinking water management.