When and where are abstractions and wastewater discharges crucial for streamflow modelling? Lessons learnt from large sample analysis and hydrological modelling in England

Water resources are increasingly under threat across the UK. Climate change is driving more frequent and severe floods and droughts, while anthropogenic pressures such as abstractions and wastewater discharges are increasingly impacting streamflow. Accurate hydrological simulations are critical for water resources management, particularly in densely populated and water-stressed regions such as South-East England. However, many hydrological models omit or oversimplify key human activities such as surface and groundwater abstractions and discharges from wastewater treatment plants, limiting model performance in human-influenced catchments.

To address this challenge, we exploit a unique water resource management dataset, which includes decades-long records of monthly surface water and groundwater abstraction (1999–2023) and daily wastewater discharge time series (2005–2015) for thousands of locations across England. We first analyse this dataset to identify when and where river flows are most affected by abstractions and wastewater discharges, and characterise their intra-annual and interannual variability, providing evidence for integrating these data into hydrological models. We then implement water abstraction and wastewater discharge modules within the DECIPHeR-GW hydrological model, and quantify the resulting improvements in streamflow simulations. We also identify the conditions under which neglecting these processes leads to substantial model degradation. Scenario-based experiments are used to assess how water resource management data should be represented, for instance, the importance of temporal patterns, providing guidance for modelling human impacts in data-scarce regions.