Simulation Research Of Agricultural Non-Point Source Pollution In Shitoukoumen Reservoir Catchment

At present, agriculture non-point source pollution has been one of the main reasons for causing environment deterioration with the efficient control of point source pollution. Therefore, the research of mechanism and domination for agriculture non-point source pollution should be taken special attention. The Shitoukoumen Reservoir is a significant water source for Changchun City and is related to economy development of Changchun City and citizens drinking water safety, it has an irreplaceable status for Changchun City's water supply and the water quality appears a very outstanding rule. In resent years, in the water basin of Shitoukoumen Reservoir, it emerges many water pollution problems that have a direct pollution to water source and construct a huge threat to the further deterioration of Songhua River water quality. Therefore, the systemic research for water environment of Shitoukoumen Reservoir, especially non-point source pollution, it has a profound realistic significance for ensuring satisfy the request of water safety and agriculture production.The natural resource and agriculture productivity are investigated in this paper, and following several aspects which concern to simulation research of Shitoukoumen Reservoir water basin are studied which based on the methods of combination of qualitative and quantitative analysis qualitative and quantitative analysis, combination of field investigation and indoor experiment.At first, the water quality of Shitoukoumen catchments'surface water environment during 2001 to 2007 is assessed by single factor method and comprehensive pollution index method, and determined the main pollution source which causing the pollution of Shitoukoumen Reservoir water basin environment, discuss the changing rule in temporal and spatial and its forming reasons through principal component analysis method and factor analysis method. The statistic analysis of water environment conventional monitoring data during 2000 to 2007 shows that during 2001 to 2004, the water quality of the reservoir belongs to class 2 which has a steady and good quality, during 2005 to 2007, the water quality of the reservoir belongs to class 3 which effected by the factors that industrial waste water and domestic waste water of upstream and soil erosion, etc. the water quality has been polluted slightly and represent a tendency of increasing year by year, and the main pollution factors are the TN and TP that causing water eutrophication. During 2001 to 2007, the average quality of Shuangyang River belongs to class 4, even to class 5, and it cannot satisfy with the request of water environment function. The water quality of Chalu River belongs to class 2 or class 3, which has a best water quality. Through it is analyzed to the pollution of surface water in the study area by the factors, it shows that the non-point source pollution of Shitoukoumen Reservoir water basin is the one of the main reasons for causing study area surface water pollution.In the Shitoukoumen Reservoir water basin, selecting representative land for constructing monitor areas, According to the synchronization monitoring result of surface runoff quality which product in the representative land using method-use type, the precipitation is apparent positive correlation to the output of TN and TP, the more rainfall producing more runoff, and more output of total nitrogen, soluble nitrogen, total phosphorus and soluble phosphorus; thereinto, Nitrogen is loss in terms of soluble nitrogen which is consistent with the trend of TN to precipitation; Phosphorus is loss in terms of bound phosphorus, and the concentration of TP is change with precipitation, the average concentration of TN and TP has a large spatial variability with the precipitation in different land-use type. The concentration of soluble phosphorus has a little changing range which represent stable basically, and there is a large difference in the average concentration of TN and TP among different land-use tpye, view as a whole, the output of TN concentration satisfy with this relation: paddy> maize field> badlands>forest; and the output of TP concentration satisfy with this relation: maize field > paddy > badlands>forest. Therefore, under different land using methods, the output of nitrogen and phosphorus is influenced by many factors, such as precipitation, fertilization quantity, vegetation cover, topography gradient, etc.The hydrogeology condition, soil character, and agriculture crop condition of study area is comprehended through the data collection and field investigation in the water basin, and the land-use type and spatial distribution of study area are analyzed by remote sensing interpretation and GPS technology, combined with Jilin province land using material and field survey. The spatial data base of agriculture non-point pollution is constructed by the overlay analysis of non-point pollution spatial information which base on GIS technology.The simulation model of agriculture non-point source pollution in the basin of Shitoukoumen Reservoir has been constructed by the AnnAGNPS model, and the simulation model is calibrated and verified by single rainstorm event. The verification result shows that the simulation precision of the simulation models for pollution mass loading in Shitoukoumen Reservoir water basin is: TN output>TP output>soil output. The model have a good simulation precision on the TN loading simulation, and a common simulation precision on TN and soil loading simulation which caused by the coarse particle is deposit in the process of migration. View as a whole, the model-AnnAGNPS can simulation the output of pollution mass in the water basin of Shitoukoumen Reservoir commendably, its simulation result can represent the agriculture non-point pollution condition.The TP, TN, soil output of Shitoukoumen Reservoir water basin is simulated by the verified AnnAGNPS model, the result shows that the study area has a soil loss of 1081.01 thousand tons in 2007, and the TP loss is 320.75 tons, TN loss is 5835.17 tons. In terms of loss type, nitrogen is loss mainly by soluble nitrogen which account for 86.3% of TN loss; The loss of phosphorus is mainly absorption phosphorus which account for 55.9% of TP loss. In terms of time distribution, affected by fertilization time and precipitation, the loss of soil, TP, TN are mainly concentrated in the high water season: July and August, which emerges a peak value in July that has a largest precipitation. In terms of spatial distribution, the loss of soil, TP, TN have a comparability in some extent that represent a big difference in spatial distribution in area, the loss quantity per unit area in forest is smaller relatively than that of plantation area and agriculture area.The main sensitive factors are calibrated and determined by the parameters sensitivity analysis and response condition of output. Eight parameters that may produce apparent effect to the output of soil, TN, TP in water basin are selected for sensitive analysis, which are: SCS curve value-CN; soil erosion factor-K; Manning roughness coefficient-MA; water and soil conservation factor-P; crop management factor-C; gradient-L; slope distance-S; fertilization quantity-PERT. The analysis shows that the output of soil, TN, TP have a different react to those parameters: SCS curve value-CN and fertilization quantity-PERT have an apparent effect to the output of TN, topography slope factor-S is in the second place, others parameters have a few impact; SCS curve value-CN and topography slope factor-S have an apparent effect to the output of TP, fertilization quantity-PERT is in the second place, others parameters have a few impact; SCS curve value-CN and gradient distance-S have an apparent effect to the output of soil, soil erosion factor-K, crop management factor-C, water and soil conservation factor-P, slope distance-S in the second place, others parameters have a few impact.The key source region of agriculture non-point pollution in the study area is calibrated by the simulation result of the model. There is some comparability between the loss of TN and TP in the study area, some distributed in aged agriculture area which furrow all year, some distributed in the middle stream of Yingma River, the others distributed in the sloped cultivated land, which show that the loss of nitrogen and phosphorous is influenced by the factors of source and migration of pollution.The control and management measure of Shitoukoumen Reservoir water basin agriculture non-point pollution are made in local conditions through the analysis of distribution character of key source areas of nitrogen and phosphorus and the sensitive factors, and from the aspects of non-point pollution source and migration route. And the effect of cultivation management measure for the output of agriculture non-point source pollution which under the measures of reducing fertilization and conversion of cropland to forest is quantitative analyzed by adjusting the parameters of the model-AnnAGNPS.