| With the effective control of industry point source pollution, the non-point source pollution has already become main pollution source in water environment nowadays. However, the land use is the main affecting driver of non-point source pollution. Different land use activity and management mode are able to lead to soil erosion and the nurture loss with surface runoff , which form the large area non-point source pollution to watershed.Shaanxi HeiHe diversion project is the main water supply source in Xi′An City. Its water quality and water quantity is related to the healthy of 3 million citizens and society economy sustainable development of Xi'An City directly. The water source area lies deep Qinling north mountain area, the slope is steep and the soil is infertile in the area. The peasant of perch for generations can only depend on "extensive cultivation" to maintain a living. Thus the non-point source pollution from cultivation activity is the main pollution source of the water source area. Therefore, studying the non-point source pollution based on different land use pattern and putting forward land use optimization management mode and measures of non-point source pollution control have practical signification in protecting HeiHe water source.Through union technique means of GIS and the environment model (SWAT2000), this study discusses the relationship between watershed land use and the non-point source pollution. By establishing basin optimization model of harmonization between environment and economy, this study discusses the best management pattern of land use. Accordingly, this study proposed the solution countermeasure of non-point source pollution control. The main content and innovative achievements are as follows:1. The foundation database of Heihe watershed non-point source pollution research is established. Using the ARCGIS software and the ArcView expansion module as platform, this study establishes DEM. Two period land use type maps (2000 and 1976) are acquired using remote sensing interpretation software ERDAS8.5. The soil type map is acquired by digitizing the Heihe rivers watershed 1: 2000 soil type map. Consequently, the foundation databases for the non-point source pollution research. are provided.2. Through SWAT2000 model adjusting, simulating and verifying, the serviceability and reliability ofSWAT2000 model are analyzed and evaluated in heihe river watershed. The results of the research show that the simulate error of hydrology part is within 15%, the calculation error of Sedimentation is within 20%, and the error of every main non-point source pollution is within 25%, which has satisfied the request of model adjust. Such indicates that the model has certain precision after calibration, which can be applied to the research of non-point source pollution.3. Using runoff-deduction method estimates the non-point source pollution load. Based on the traits of NSP affected by rain-runoff process and NSP being closely correlative with runoff, the runoff-deduction method is proposed. By this method, the monitored water quality data is divided into point source pollution and non-point source pollution.4. Through the quantitative study of non-point sources pollution loading of 5 scence of land use, the impact of land use to non-point sources pollution is analized. On the base of calibrating model parameter of SWAT2000, land use can be considered from deterioration or improvement and divided into 5 land use scenes. The non-point source pollution loads under 5 land use scenes are simulated by SWAT2000 respectivily, and the results of simulation are compared and analyzed. The results shows(:1) Forestland can reduce non-point sources pollution loading effectually. (2)the total nitrogen and total phosphorus loads is respectively 173.334 t and 38.653 t under present land use condition t. There is potential threat in the basin water environment. The protection key of water environment is reasonable land use and effective land magement in the future. (3)when land use of the heihe river watershed worsens and becomes into the scence of hongcaohe river watershed, the water quality of the area will be deteriorated greatly. On the contrary, with the implementation of the policy of watershed forest protect project, the area of forest land will be a gradual growth and the environment of watershed will be also improved. (4) Combining theory with practice, in order to improve the water environment of watershed and control effectively non-point source pollution, the future land use should attain the best condition that slope field above 15°should completely return to forests, allowing a few farming land in the slope field under 15°, unused land inexistence, vegetation cover being well. Under the scene of land use, the non-point source pollution nitric unit-load of forest land is 0.67kg/ (hm2·a), the non-point source pollution phosphorous unit-load of forest land is 0.11kg/ (hm2·a), the non-point source pollution nitric unit-load of cultivated land is 2.73kg/ (hm2·a) and the non-point source pollution phosphorous unit-load of cultivated land is 1.38kg/ (hm2·a).5. The reasearch on regional land use change trends and non-point sources pollution. Combining model simulation with landscape ecology, this study discusses the impacts of land use to non-point source pollution in recent 25 years, which draws such conclusion: (1)The trends of land use change are developing towards the more reasonable and more advantageous direction in protecting water environment. (2) Forest land areas have been expanding every year. The cultivated land and unused land are reducing gradually. The rationalization degree of land use is advanced greatly, but the change of land use distributing proportions in the different slope grades is not obvious. And the areas of resident and industry-mining land are increasinggradually. The water environment faces a potential danger. To protect water source region, population removing police should be carried out, the efforts of tree planting and water source protection should be intensified, mining industry and man-made effect should be limited, and government should exert continually leading action to lead dweller using land more advisablely, especially above 15°.6. The watershed optimization method about land-use, economic and environment is set up. On the base of scence simulating of land use, considered the local economical produce, the optimization method about land use, economy and environment is set up. The calculation results indicate that the sloping field above 15°will be completely returned to forest, the farm land in slope field below 15°is not more than 4.24km2 , unused land is not existent, and the vegetation coverage is very well.7. As far as land use and management of watershed is concerned, the measures of non-point source pollution control are put forward. Based on the trait non-point source pollutant load being closely related to human activities, the measures of non-point pollution control are proposed. |
PDF Full Text Request