Applying water environment capacity to assess the non-point source pollution risks in watersheds

Area of Science:

• Hydrology
• Environmental Science
• Water Resource Management

Background:

• Effective non-point source (NPS) pollution management is crucial for watershed water quality.
• Existing NPS pollution risk assessments often overlook the influence of water functional zones (WFZ) and varying water environmental capacities.
• A comprehensive approach is needed to accurately assess NPS pollution risks in diverse watershed conditions.

Purpose of the Study:

• To develop and apply a novel NPS pollution risk assessment method integrating WFZ, receiving water body environmental capacity, and pollution load dynamics.
• To quantify the impact of sub-catchment pollution discharge on downstream water quality.
• To improve the scientific basis for NPS pollution control and management in watersheds.

Main Methods:

• Utilized the Soil and Water Assessment Tool (SWAT) to model NPS nutrient loss processes.
• Integrated WFZ, environmental capacity, and space-time pollution load data for risk assessment.
• Applied the method to the Le'an River Watershed at annual and monthly scales.

Main Results:

• NPS pollution risk exhibits significant seasonal and spatial variability.
• Water environmental capacity is a key factor influencing pollution risk levels.
• High pollution loads do not always equate to high risk; low loads do not guarantee low risk.

Conclusions:

• The proposed NPS risk assessment method effectively quantifies pollution impacts by considering environmental capacity.
• This approach can differentiate risk levels masked by similar pollutant loads or water function zones.
• Accurate NPS pollution management requires risk assessments that account for spatial, temporal, and capacity-based factors.