GIS-AHP Ensembles for Multi-Actor Multi-Criteria Site Selection Processes: Application to Groundwater Management under Climate Change

A possible adaptation pathway for water suppliers in Germany who face a climatically driven increase in water stress is the development of aquifers which are not used at their full potential. However, identifying suitable sites for aquifer development can go along with severe conflict potential due to the great variety of stakeholders who are involved in the decision-making process. We approach this multi-actor and multi-criteria decision-making problem by developing a geoinformation system-based analytic hierarchy process ensemble (GIS-AHP ensemble). As opposed to the classic GIS-AHP method that yields ratings of site suitability based on a single expert evaluation, the here proposed new GIS-AHP ensemble method respects multiple expert evaluations and allows for quantifying the robustness of yielded site ratings in multi-actor contexts, which helps to mitigate conflict potential. The respectively derived GIS-AHP ensemble site ratings for northwest Germany are successfully checked for plausibility in the framework of the study by using long-established groundwater abstraction areas as indicators for good site conditions. The GIS-AHP ensemble site ratings are further tested regarding their usability for long-term water supply planning by integrating a groundwater recharge scenario under climate change for the period 2020 to 2050. The proposed GIS-AHP ensemble methodology proves useful in the given case study for fostering integrated environmental decision-making and exhibits a high transferability to other, thematically differing site selection problems.