A Process-Based Model to Track Water Pollutant Generation at High Resolution and Its Pathway to Discharge

The estimation of water pollutant loads is of crucial importance as it decides data inputs for both subsequent water quality models and watershed pollutant mitigation strategy. However, the generation of water pollutant loads at high resolution and the life-cycle pathway of them from sources, through pipelines and wastewater treatment plants, finally to recipient water bodies remain unclear. This study aims to establish a process-based Water Pollutant Loads Tracking model and applies it to a rapidly urbanizing watershed in Taihu Lake Basin, China at the resolution of 5 m x 5 m in 2017, whose terrain is flat, slowly lowing from west to east. Results show that, of 261.55 tons of the total phosphorus (TP) generation, 71.28% is collected, and 64.32% is treated, with only 26.46% discharged to the water bodies and 1.25% to the target ones. The spatial hotspots of TP generation are mainly concentrated in residential and industrial areas. Direct discharges from point sources and nonpoint runoffs, especially in rainy seasons, are recognized as the main challenges for local water pollution control. The main innovation of this study is to quantify the generation of water pollutant loads at high resolution and to trace the subsequent pathway to collection and discharge, and then to identify the potential substantial gap between generation and discharge, demonstrating the efficacy and broader applicability of this model. A process-based mass balance model is developed to quantify the generation pattern of water pollutant loads at high resolutionThe model is a reliable tool for tracing water pollutants from sources to recipient water bodies without any topographic limitationSubstantial positive gap between generation and discharge indicates the effectiveness of local pollution control measures

Automated summary

The estimation of water pollutant loads is crucial for water quality models and pollutant mitigation strategies. This study develops a process-based Water Pollutant Loads Tracking model and applies it to a rapidly urbanizing watershed in China. The results show that point sources and nonpoint runoffs are the main challenges for local water pollution control. The study's innovation lies in its high-resolution quantification of pollutant generation and tracing of the pathway from sources to recipient water bodies, demonstrating the model's effectiveness and broader applicability.