| Lakes, water reservoirs, and streams, which are the most valuable sources of drinking water for the earth's population, are vulnerable to pollution and degradation of water quality, particularly to eutrophication. Accelerated eutrophication of lakes and reservoirs is the most serious degradation of water quality in China during the last decades. With the effective control of industry point source pollution, the agricultural non-point source (NPS) pollution has already become the main pollution source in water environment nowadays, which resulted in Water body worsen and Lake deteriorated. Therefore, it has the important theoretical and practical significance to control agricultural NPS and protect the ecological environment for the development of the agriculture, resource and environment.With the development of economy and society, the issue on water eutrophication becomes one of the greatest challenges in the third largest fresh lake in China, the Taihu lake.90 percent of the river network in HangJiaHu region, Zhejiang province, one of the eight water system in the Taihu basin, do not meet the need for the water function. Also the water quality of the Jinghang canal in the Zhejiang province do not attain the water quality standard for grade III. Nitrogen and phosphorus losses in agricultural non-point source has been attracted more and more attention since it becomes one of major factors in resulting in eutrophication of surface waters after controlling the industry and urban point source. An interdisciplinary exploration of the intersection among hydrology, geography, landscape ecology and environment science is encouraged. We researched on the agricultural NPS simulation in HangJiaHu area with the integration of the Geographic information system (GIS) and environmental model. Moreover, we analyzed the dynamic change of land use and landscape pattern based on the point of view for environment science and landscape ecology. Finally, We advanced the best management technology system and optimized the landscape pattern which has the very realism significance for protecting the water environment. The main content and results are as follows:1,The foundation database of HangJiaHu region non-point source pollution simulation research is established. Based on the remote sensing and GIS, we built the spatial database including the Digital Elevation Model (DEM), two different periods land use/land cover type maps, soil type map. Moreover, we built the attribution database including the collecting data, investigation data and observed data outside and the data in the lab.2,We investigated the agricultural non-point source pollution in HangJiaHu region and analyzed spatial and temporal distribution of nitrogen and phosphorus pollutants in the typical Jiaxing segment of Jinghang canal. Based on the GIS technology, we analyzed the pollution sources and defined the agricultural NPS percent in the study area. Our results showed that nitrogen and phosphorus loss from agricultural fertilizer to the water environment is far larger than those of sewage and livestock. The losses order is agricultural fertilizer> livestock> sewage. In the HangJiaHu region, nitrogen and phosphorus loss from Jiaxing city to water environment is larger than the other areas. NH4+-N emissed mostly in Jiaxing and Yuhang. We selected the Jiaxing segment water of Jinghang canal as the experiment field where we surveyed the water pollution environment, monitored, sampled and laboratory experiments. The results showed the larger value of NH4+-N appeared in April, July and September to October in the temporal distribution. The largest value appeared in July. In the spatial distribution, the water in the vicinity of the residential areas, farms and breed fields were more seriously destroyed. The different land use types in conservation directly affect the different levels of nutrients for contributions of water pollution.3,Through SWAT model adjusting, simulating and verifying, the service ability and reliability of SWAT model are analyzed and evaluated in HangJiaHu region. In this paper, based on the landform, we divided Hangjiahu region into two parts, one as the west hill area of Hangjiahu, and the other as the east plain river network. Thus, the result showed the representation in the different landform. We considered sensitivity analysis for the specific parameters of the model, the results indicated:sensitive parameter which has the greatest influence on the runoff is Curve number (CN2), Soil available water content (Soil_AWC), Soil evaporation coefficient (ESCO). Moreover, based on the 2002-2005 observed data, these parameters were calibrated and validated for the surface runoff volume and nutrient loads in HangJiaHu region. Coefficient R2 and Nash-Suttcliffe coefficient E were selected to evaluate the simulation results. Simulated results closely matched with the observed data. It confirmed that SWAT model could simulate runoff and nutrient loads quite well, particularly in this complex region.4,Based on the spatial and temporal changes of land resources amount, land use degree and transition of land use types, this paper analyzed land use structure and dynamic change of land use types in the HangJiaHu region. Land use types in the HangJiaHu region focus on farmland and woodland which area diminished in 2000-2004. The main features of land use types in the western hill area of Hangjiahu region are:the increased area of urban land was the largest in the land use types whose areas increased, followed by Dry land and Water body between 2000-2004. The main features of land use types in the eastern plain area of HangJiaHu region are: Urban area has the highest increase in all the land use types for the increasing area, followed by Water body between 2000-2004. However, farmers' settlement, Paddy fields and Dry land area reduced during this period. Land use changes were mainly Urban land, Paddy land and the Residential area in rural areas between 2000-2004. At the same time, the area of Water body changed largely with serious soil erosion. The transition between land use types has occurred mainly as:the paddy land were converted to Forest land, Urban land, Water body, Dry land and Farmers' Settlement.5,As far as the landscape grid maps in 2000 and 2004 period is concerned, we selected the landscape indice such as patch density, patch number, shape index, and the largest patch index (LPI) to analyze the landscape pattern. The results showed patch density, patch number and shape index appeared the increase trend, the largest patch index (LPI) indicated the reduce trend. It suggests the whole landscape had a fragmentation trend. 6,Based on the spatial distribution pattern of land use types for HangJiaHu region, it showed the farm land and urban land in the eastern plain river network are the main land use type playing the role of "source". The amount of pollution from the "source" is relatively large. Therefore, the surface water quality of Eastern plain area was poor. While most of the mountainous and hilly areas in the western area of forest land, play the role of "load", which works with the intercept or filtering functions. Consequently, the surface water quality in the western is better than that of the eastern of the study area. The function of the "source" and "load" in the landscape has great impact on the nonpoint source. "Source" makes a function for making pollution and "load" make the function for the transportation. The results give a good advice for controlling the water pollution and protecting the water environment.7,As far as the HangJiaHu agricultural non-point source pollution characteristics is concerned, we analysed the best management technology system to measure non-point source pollution control which has been put forward. We also proposed the optimizing landscape project for the policy and management department integrated with the view of landscape ecology.
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