Study On Agricultural Non-Point Source Pollution Of Wuchuan Catchment In Upstream Jiulong River

Jiulong River is an important drinking water source for the cities of Longyan, Zhangzhou and Xiamen. At the same time, this basin is also a coastal one. At present, non-point source pollution, especially agricultural non-point source pollution in the upstream has been particularly significant, so study on non-point source pollutant losses from agricultural catchment in Jiulong River basin have important realistic meaning and theory value.Wuchuan catchment in the upstream of Jiulong River has been selected as a study site. A large number of basic data were collected through the extensive on-site investigation. Surface runoff, water quality and underground water quality of different land-use were determined for rainfall events occurred during the whole year 2002. According to the works mentioned above, achievements have been described as following:1. Characteristics of nitrogen and phosphorus losses from Wuchuan catchment were discussed.To Wuchuan catchment, nitrogen and phosphorus losses occurred between July and September. More than 95%, 87% and 93% of total loads of total nitrogen, total phosphorus and sediments, respectively, are lost during this period. Dissolved nitrogen was predominant form in surface runoff. Total phosphorus lost mainly in particulate form.2. Characteristics of nitrogen and phosphorus in leaching were discussed. The concentration of nitrate nitrogen is higher than ammonia nitrogen andthe main type of nitrogen in the leaching water is nitrate nitrogen in the Wuchuan area where high amount fertilizers were applied and low water table was appeared. But the concentration of ammonia is higher than nitrate in the land where the organic fertilizers were applied during some period. The concentration of ammonia nitrogen is very high in this area.3. A water balance method has been adopted in order to estimate the nitrogen leaching amount in the field. The leaching loads of inorganic nitrogen range from 3.7 to 54 kg/ha.a in the research area, the banana field has the highest load of inorganic nitrogen in leaching, the paddy is the next, the grass is the last.4. This paper systematically and completely adopted the AGNPS model tostudy the non-point source pollution in the agricultural watershed of Fujian.Quantities of nitrogen and phosphorus loads were determined using validated AGNPS model when studying the non-point source runoff of agricultural area. Total nitrogen loss is 27.5kg/ha-a, total phosphorus loss is 0.75kg/ha-a in Wuchuan watershed. Soil erosion contributes to 19.67% of total nitrogen losses, 88.64% of total phosphorus losses; fertilizers contribute to 80.33% of total nitrogen losses, 10.70% of total phosphorus losses.5. AGNPS model has been used into the management practices evaluation. Several scenarios have been made quantitative assessment with the AGNPS before and after applied, this method gives the scientific basis for NPS pollution controlling measures.