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Spatial Distribution Characteristics of Non-Point Source Pollution of Xingkai Lake Irrigation District Based on L-THIA Model

Agriculture has been identified as the largest contributor of non-point source (NPS) pollution of surface and ground water systems globally. Estimation of non-point source pollution under different land uses is an important task in non-point pollution control in China. Taking Mishan city in Xingkai lake irrigation district as the study area, with the help of GIS and RS technology, the long-term average pollution loads in Mishan city were estimated using the Long-Term Hydrologic Impact Assessment (L-THIA) model. The spatial distribution characteristics of the pollutants were analyzed, including total nitrogen, nitrate nitrogen, total phosphorus and suspended solids. Results indicated that the spatial distribution of the four non-point pollutants is quite identical. The total loads of four pollutants were different under different land use types, and the agricultural land had the most important impact on non-point pollution in the study area. Forests and grassland contributed more to the retention of the pollutants in this area. The result of this research showed that L-THIA model is available for the spatial distribution of non-point pollution and it can provide the service for planning and management of the watershed.