太湖流域营养盐产量演变和趋势的数值模拟研究

NUMERICAL SIMULATIONS ON CHANGE AND TREND OF NUTRIENT PRODUCTIONS FROM TAIHU LAKE CATCHMENT,CHINA

认识流域湖泊水体富营养化的演变和趋势是湖泊污染控制和治理中的重要研究课题。本文将在分析和论证太湖流域营养盐自然本底、人类活动作用急剧增加的近50年来太湖流域营养盐的变化情况、以及全球气候变化和流域经济发展未来30年太湖流域营养盐变化趋势等三方面的基础上，对太湖流域营养盐产量变化做出评估和预测。研究表明，在未来气候变化概率分析和区域经济发展规划基础上，太湖流域未来30年营养盐流域产量将比现代（2000s）增加25％～33％，这将增大太湖水体污染的压力。

For a better control and treatment of lake pollution, it is important to recognize the changes, procedures, and trends of water eutrophication in Taihu Lake catchment,a developed area of 3.6 ×10^4km2 with a population of 0. 4 × 10^8 in China. Based on both data of the meteorological-climate,hydrology,and water quality and of social economic statistics,this paper used the SWAT model, a catchment nutrient model that can examine the lake eutrophic changes,to evaluate and predict the changes of nutrient productions of Taihu Lake. Databases of topography, soil and land use, the point and non-point sources of sewerage, industrial sources, livestock drainage, soil nutrients, and losses of fertilizers in drained agricultural lands were constructed ,while the nutrient sedimentations of total nitrogen （TN） and total phosphorus（TP）were simulated through a boundary condition prescription for the Taihu catchment. We designed three experiments for the following three periods ： the baseline of nutrients and their changes under a natural agricultural condition during the past 200 years, the changes of nutrients under the pressure of increased human activities in the industrial and urbanizational conditions during the past 50 years, and the prediction of nutrients controlled by global climate change and regional economic development for the future 30 years. The simulations for the past 200 years were designed for the pre-industrial boundary conditions,which were based on sedimentary pollen data and climate parameters from long-term observations of three stations surrounding the catchment. The results confirm that modeling can capture basic features of nutrient development. The average TN of the Taihu Lake was 1860t/a with the variability between 640t/a and 4100t/a; and that of TP was 240t/a with the variability between 60t/a and 580t/a. The average TN concentration can be compared in a broad scale to the sample values which were taken from sedimentary cores of the past 100 years from the Taihu Lake. When inputting industrial point pollution discharge ,the loss of agricultural fertilizers ,urban sewerage ,and livestock drainages in the boundary conditions,the simulation shows that TN production was 8084t/a and TP was 787t/a during 1962-1965,and during the 1990s TN production was 10000- 40000t/a and TP was 2000- 9000t/a. The sensitive experiments show that domestic sewage and industrial point sources are the main nutrient sources. By the Monte-carlo probability model, we analyzed the future temperature and precipitation and drove the SWAT- model for the future 100-year experiment for the Taihu catchment. The plan of regional economic development is also included for experiments. The simulations for the future 100 years show that,the nutrients during the future 30 years will probably increase to 1975 -3155t/a of TN and 242 -397t/a of TP,mainly caused by climate forcing,equivalent to 5% - 10% increase compared to the present time of the 2000s. They will increase to 8000 -10100t/a （TN）and 400- 500t/a （TP） ,mainly by human activities,equivalent to 25% -33% compared to the 2000s. This nutrient inputting to the/ake would largely increase the pressure of water pollution of the Taihu Lake. Key words