Drivers and barriers for taking account of geological uncertainty in decision making for groundwater protection

Abstract The geological conceptual model is considered a major source of uncertainty in groundwater modelling and well capture zone delineation. However, how to account for it in groundwater policy and management remains largely unresolved. We explore the drivers and barriers to account for geological conceptual uncertainty in groundwater protection amongst decision makers and stakeholders in an agricultural groundwater catchment in Denmark. A groundwater model is used in an explorative manner to analyze the impact of alternative geological conceptual models and hydraulic conductivities on capture zone delineation. A focus area which covers multiple modelled capture zones is defined and considered for groundwater protection. Model uncertainty and focus area are discussed at two workshops, one with local farmers and another with local and national stakeholders. Identified drivers to account for model uncertainty include: i) more robust drinking water protection by considering a larger area for protection than identified from a single geological model; and ii) stability over time of management plans. The main barrier is economical, as groundwater protection on a larger area would lead to immediate additional costs. We conclude that integration of geological uncertainty in groundwater protection plans may be improved through: i) better communication between the research community and the national water authority; ii) more constraining guidelines regarding the estimation of geological uncertainty; and iii) the development of frameworks ensuring knowledge transfer to the local water authorities and detailing how to integrate uncertainty in management plans.