Identification of non-point source pollution emission characteristic based on fine detailed analysis of inflow pollution load

Abstract

[Objective] This study aims to clarify the structure of non-point source pollution in the watershed and conduct a detailed analysis of the spatial and temporal characteristics of non-point source pollution loads. [Methods] The SWAT(Soil and Water Assessment Tool) watershed non-point source pollution model was used as a basis., Representative hydrological series wereas selected, and combined with an inflow pollution load calculation model., A technical process was developed to identify key non-point source pollution areas based on pollution load and inflowintensity. This process was verified in the Shahe Reservoir watershed, where data conditions were relatively complete. [Results] The results showed that the total inflow load of total nitrogen(TN) in the Shahe Reservoir watershed was found to be 198.34 t/a, with non-point source pollution accounting for 86.53% of this load. The largest contribution to the TN load came from tea gardens in the watershed, contributing 23.84%. The TN load during wet years and extremely wet years increased by 58.06% and 289.09%, respectively, compared to dry years., During the wet season, the average monthly TN load was 75.24% and 372.51% higher than in the normal and dry seasons, respectively. The river reduced the TN load by 33.58 t/a, with a reduction ratio of 14.48%. The variation in TN inflow pollution intensity across sub-watersheds ranged from 0.36 t/km² to 4.73 t/km². The low-value zones for non-point source pollution emissions were primarily located in the southern part of the watershed, while the high-value zones were concentrated near the reservoir. The incflow TN intensity per unit area in the Shahe West and Shahe East control sub-zones was significantly higher than in the southern part of the watershed. [Conclusion] Pollution control efforts should be strengthened in areas with high pollution yieldss, high pollution regions, and during high pollution periods. The established technical process can effectively identify and scientifically analyze key non-point source pollution areas in the watershed, providing technical support for non-point source pollution prevention and ecological adaptive development in watershed water environments. This will ensure more targeted and effective pollution control measures.

Keywords

non-point source pollution / SWAT model / total nitrogen / characteristic identification / Shahe Reservoir