Socio-hydrology of long-distance water transfers in Germany

Abstract

Ensuring robust drinking water supply under climate change and both shrinking rural and growing urban settlements as well as further behavioral changes is a pressing global challenge. Though current climate models estimate that water availability in Germany will not change significantly in the long term, short to medium term drought periods are a critical threat to constant drinking water supply. Recent analyses suggest higher peak demands by private households in dry and hot summer periods, which may intensify water use conflicts with other sectors. To address these challenges, long-distance water transfers or so-called intra- and inter-basin water transfers are discussed as major supply-side solutions to balance water-deficit and surplus water regions. While the German law prescribes to use locally available water resources first, already today 20% of drinking water in Germany is transported over large distances. Against this background, we will present the first comprehensive socio-hydrologic investigation into the historic development of long-distance water transfers in Germany with a focus on dynamics, feedback mechanisms and spill-over effects. Based on a qualitative content analysis of case studies and quantitative data compilation we build social-ecological system dynamics models to illustrate our findings that long-distance water transfers are likely to inherently expand due to their technical, institutional and discursive effects on debates and planning processes around water supply. We complete our contribution by coining a new definition of long-distance water transfers that is more appropriate to catch the specific characteristics of surface-based, centralized water supply over large distances compared to decentral, groundwater-based and local water supply infrastructure. We suggest acknowledging the infrastructure’s effect in shaping water supply systems and the diverse effects on local water resources and municipalities along the ways.