【摘要】 湖泊-流域构成的复杂系统是湖泊富营养化研究的热点。应用SWAT模型对长江下游太湖流域上游外源氮、磷入湖通量进行模拟,以反映陆源入湖氮、磷营养盐的通量、空间分布和时间变化情况。以水文模拟为基础,引入相关系数(R)和Nash-Sutcliffe效益系数(Ens)评价模拟结果。水文模拟率定期月均值R多在85%以上,Ens在0.24~0.90,模拟年平均径流量相对误差为3.2%。验证期各站月均值R均在80%以上,模拟年总量误差为8.1%。模拟结果显示,流域多年平均径流量为104.15×108 m3,营养盐输出浓度浙西区TN、TP分别为2.38mg/L、0.18mg/L;湖西区分别为5.68mg/L、0.43mg/L;武虞锡澄区分别为6.14mg/L、0.40mg/L。流域营养盐多年平均入湖通量TN为42 730t/a,TP为3 075t/a,2000年开始,流域TN、TP的入湖通量均有下降趋势。流域营养盐具显著空间差异,陈东港-大浦口、小梅口-长兜港、武进港-直湖港是最主要的入湖通道,贡献率分别达到27%、24%和20%,应作为流域外源营养物质管理和控制的重要区域。更多还原

【Abstract】 Nutrients(mainly as nitrogen and phosphorus)transported from watershed is one of the most important nutrients sources for lake eutrophication.Assessment and control of the watershed exogenous nutrients has been the key to resolve the problem of lake eutrophication.The Taihu Lake Basin,located at the lower-reach of the Yangtze River,with a watershed area over 36,000km2 was chosen as the study area for its serious eutrophication.Precious studies of this area were either on small scale of sub-watershed simulation,or using monitored data to estimate the nutrients loading statistically.Numerical simulation over all the upstream has seldom been done before.In this study,the watershed distributed hydrological model SWAT 2005(Soil Water Assessment Tool)was applied to simulate the watershed nutrients transportation during 1987-2007,to assess the nutrients transportation trend,spatial and temporal distribution.Database composed of topography(1∶250 000),climate(daily precipitation,temperature,humidity and wind speed),hydrology(flow speed,flow flux),soil(1∶1000 000 with physical and chemical properties),landuse/cover(1∶100 000)and variety of nutrient sources were established to simulate the nutrients loading.Both natural process and human activities within the basin were considered,such as reclamation of lake,the construction of reservoirs.And the simulation was divided into two experiments.The hydrological simulation was the most basic one,and then the nutrients simulation,with background,non-point source pollution(agricultural),and point source pollution were added and simulated in a specific sequence.Data from hydrological gauge station and the monitored data were used for the validation and calibration of simulation.Correlation coefficient(R)and Nash-Sutcliffe efficiency coefficients(Ens)were introduced to evaluate the simulation results.In calibration,the correlation coefficients of average monthly value were all over 85%,the efficiency coefficients were between 0.24 and 0.90,and the relative error was3.2%.In validation period,the correlation coefficients of average monthly value were all over 80%,and the relative error of annual value was 8.1%.And both the hydrological and nutrients simulation could match well with the data in references.The simulation results showed that the annually averaged runoff of the Taihu Lake Basin was 104.15×108 m3.The nutrients production was 42 730t/a for TN,3 075t/a for TP,with a trend of decreasing after 2000.The simulated concentrations of TN and TP in Zhexi area were 2.38mg/L and 0.18mg/L,respectively;5.68mg/L and 0.43mg/L in Huxi area;and 6.14mg/L,0.40mg/L in Wuyuxicheng area.The simulation results futher showed a significant spatial variation.And among all the upstream input rivers,Chen Donggang-Da Pukou,Xiao Meikou-Chang Dougang,Wu Jingang-Zhi Hugang were of the most importance,with the contribution ratio of 27%,24% and 20% respectively.The area mentioned above should be regarded as the key areas for external nutrients source control.The study results could provide basic data for watershed nutrients total amount control policy.更多还原