Evaluation of a socio-hydrological water resource model for drought management in groundwater-rich areas

Groundwater is a drought resilient source of water supply for many water users globally. Managing these highly-used groundwater stores is complicated by the episodic nature of droughts and by our limited understanding of water systems’ response to extreme events. Models are useful tools to simulate a range of prepared drought interventions, however, we need to ensure robust representation of surface water and groundwater storage, users of both resources, and associated management interventions for drought resilience. A robust modelling approach is therefore essential for decision-making in groundwater management.

In this study, we present a Socio-Hydrological Water Resource (SHOWER) model for drought management in groundwater-rich regions. We evaluate SHOWER using a response-based and a data-based model evaluation in Great Britain which considers the modelling uncertainty, dynamic impact of management and modelling setups available. In the response-based evaluation, we first examined the model consistency with our understanding of the system functioning and evaluated the influence of modelled management scenarios in normal and droughts conditions on discharge and groundwater levels. Secondly, in the data-based evaluation we tested the accuracy of heavily influenced discharge and groundwater level simulations in three catchments representative of typical hydrogeological conditions and water management practices in Great Britain. Results from the response-based method show consistent simulations for all model setups. We identified which parameters were influential to model output at which times. Integrated water management interventions have significant impact on flows and groundwater beyond parameter uncertainty and show leverage to reduce droughts by minimising shortages in water demand. The data-based analysis shows that calibration can be focused on either source-specific or combined model outputs using a “best overall” calibration approach that captures groundwater levels and low flows. The source-specific calibrations result in the highest and narrowest KGE ranges for discharge and groundwater (KGE: 0.75–0.84 and 0.62–0.95 respectively) with larger ranges using a “best overall” approach (KGE: 0.55–0.79 and 0.27–0.91). With the modular and open-access structure of SHOWER we aim to provide a useful new tool for groundwater managers to explore management interventions further, increasing drought resilience strategies using a robust modelling approach.