Identification method and application of critical load contribution areas based on river retention effect.

Area of Science:

• Environmental Science
• Water Resource Management
• Pollutant Transport Modeling

Background:

• Critical Source Areas (CSAs) and Critical Load Contribution Areas (CLCAs) are distinct concepts in watershed management.
• Understanding pollutant transmission, including river retention effects, is crucial for effective water quality management.

Purpose of the Study:

• To develop an integrated modeling approach to differentiate CLCAs from CSAs in complex watersheds.
• To investigate the impact of river retention effects on pollutant transport and identify CLCAs.
• To provide a scientific basis for optimizing watershed management practices.

Main Methods:

• Integrated modeling approach combining the Modified Export Coefficient Model (MECM) and the Soil and Water Assessment Tool (SWAT).
• Case study conducted in the Miyun Reservoir watershed, China, a typical rural watershed.
• Analysis of pollutant sources, transport efficiency, and river network deposition.

Main Results:

• Anthropogenic pollution from livestock, rural activities, and cultivation is the primary pollutant source in most townships.
• Pollutant transport shows regular decay in efficiency upstream from the basin outlet.
• River retention significantly retards pollutant transport, with over half the load deposited in the river network.
• CLCAs are spatially distinct from CSAs, typically located in areas with high transport efficiency and pollutant load.

Conclusions:

• The integrated model effectively differentiates CLCAs from CSAs by incorporating river retention effects.
• Pollutant transmission processes, including river migration, are critical for understanding watershed pollution dynamics.
• The findings aid in the scientific configuration of management practices for improved water quality.