Abstract:
Abstract: Non-point source (NPS) pollution has been recognized as the largest threat to water resources throughout the world, and the evaluation of NPS loads is a priority in recent years. Major pollutants, particularly from agricultural activities, include nitrogen (N), phosphorus (P) and sediment that have been released into aquatic environments. It is also necessary to identify the spatial and temporal distributions of NPS pollutants and the highly polluted areas for the purpose of watershed management. Some models have been widely used at the watershed scale. However, variations in natural and social factors make it difficult to find a proper model to be used on NPS pollution management in China. The export coefficient model (ECM) has been used to evaluate the influence of NPS on total nitrogen (TN) and total phosphorus (TP) in several cases, such as the Xitiaoxi watershed in Zhejiang, the Three Gorges Reservoir Area in Hubei Province, Beijing City, Daqing City, Heilongjiang Province, which all provide important reference for NPS management. Therefore, in this paper, the ECM was used to assess the influence of NPS on N and P loading in the Xinlicheng Reservoir of Jilin Province. Xinlicheng Reservoir, one of the drinking water resource areas in Changchun City, is located in middle of Jilin Province, and its catchment area covers an area of 1970 km2 and includes 1 county, 3 districts and 2 cities. A large percentage of the population in the Xinlicheng Reservoir catchment area lives in small villages. The domestic sewage from the villages is scattered and discharged with little or no treatment. Data related to the main non-point sources were analyzed, including rural domestic wastes, distributed livestock farms, fertilizers and land use. Additionally, the potential N and P loading from NPS originated from a variety of sources were estimated and analyzed, including rural domestic waste, livestock farms, and land use. They gave the temporal distributions of the potential NPS loads within the reservoir area. In this study, the NPS pollutant load was simulated using the ECM. The results demonstrated that the TN and TP loads were respectively 2822.485 and 471.123 t/a. TN and TP loads were affected by the type of land utilization significantly. The contributions to pollution load from various types of pollutant sources were different. The magnitude orders of the contribution from various types of pollutant sources for TN and TP loads were wastewater and garbage from land use > livestock breeding > rural residents, and livestock breeding > land use > rural residents respectively. The differences among various districts about TN and TP loads and their load intensities were great. The research about the distribution of N and P pollutants and their load intensities from agricultural non-point sources can provide a foundation on regional planning and agricultural structure adjustment in study area. Furthermore, these findings demonstrate that the ECM can provide a simple and reliable approach to evaluate the potential N and P loading in the Xinlicheng Reservoir of Jilin Province and is useful for the planning and management of the local agricultural watersheds.