Integrating source-water connectivity into SWAT for hotspot-oriented nitrogen management in hilly catchments

Area of Science:

• Environmental Science
• Hydrology
• Water Quality Management

Background:

• Nitrogen pollution from agriculture and urban areas is a major challenge for water quality in hilly catchments.
• Accurate identification of pollution hotspots is crucial for effective mitigation strategies.

Purpose of the Study:

• To integrate a Source-Water Connectivity Index (SWCI) into the Soil and Water Assessment Tool plus (SWAT+) model.
• To enhance the assessment of nitrogen load distributions and identify pollution hotspots in hilly catchments.

Main Methods:

• Integration of the SWCI into the SWAT+ model.
• Simulation of nitrate nitrogen (NO3--N) and total nitrogen (TN) loads.
• Analysis of land use, soil texture, and spatial patterns of nitrogen loads and concentrations.

Main Results:

• The SWCI-SWAT+ model showed superior performance in simulating NO3--N and TN loads compared to the conventional SWAT model.
• Tea plantations and steep slopes (>40°) were identified as dominant contributors to nitrogen loads.
• High sand-content soils contributed significantly to NO3--N loads, while medium sand-content soils contributed most to TN loads.
• Distinct spatial patterns of NO3--N and TN hotspots were identified, influenced by land use and urban discharge.

Conclusions:

• The SWCI-SWAT+ framework provides an effective approach for non-point source pollution control.
• It enables accurate identification of pollution hotspots and diagnosis of load-water quality mismatches at the watershed scale.