Study Of Nitrogen Budgets In Agricultural Fields Of The Changjiang River Basin

Firstly, the study used database that are include in the Changjiang River basin′s agricultural county level data of 1990 and 2000,the same term vector data had obtained from TM remote sensing image,published conversion data from science publication,datum and IPCC and so on. And the study based on N budget change model of Changjiang River basin′s agricultural fields and by GIS technique,all counties of the Changjiang River basin N budget change had been counted, then N inputs, outputs and surpluses of the whole basin have been gathered and obtained. The results indicate that N inputs, outputs and surpluses of the whole basin are 7.65×10~6t/a, 4.23×10~6t/a and 3.42×10~6t/a respectively in 1990, in surpluses a part into waterbodies another part remain in soil, its are 2.05×10~6t/a and 1.37×10~6t/a respectively. N inputs, outputs and surpluses of the whole basin are 10.22×10~6t/a, 5.44×10~6t/a and 4.78×10~6t/a respectively in 1990, a part in surpluses into waterbodies and another part remain in soil, its are 2.65×10~6t/a and 2.13×10~6t/a respectively in 2000. Changes quantity of N input, output, surpluses, import waterbodies and remain in soil are 2.57×10~6t/a, 1.21×10~6t/a, 1.36×10~6t/a, 0.60×10~6t/a and 0.76×106 respectively in the Changjiang River basin's agricultural fields from 1990 to 2000. Because the quantity change of chemic fertilizer had been used mainly that Chongqing,Shanghai,Wuhan,Wuxi,Nanchang,Tanghe,Xinye,Xiangyang,Chengdu and Suining are important prevention and control regions of the Changjiang River basin's agricultural fields,its′non-point source N input to waterbodies change were bigger from 1990 to 2000. It will been prevented and controlled effectively that non-point source N pollution of the Changjiang River basin's agricultural fields regions. The Best Management Practices should been adopted. The BMPs can reduce non-point source N production from headstream and stream. Furthermore, it should been used that the means of relevant propagandize, rule of law, technology, economy etc, so that non-point source N pollution of the Changjiang River basin's agricultural fields will been controlled availably and assuredly.Secondly, the study used agricultural county level database of the three-gorges reservoir area from 2001 to 2005 and the same term vector data,and educed nitrogen load recently years and important prevention and control regions of non-point source nitrogen pollution of the three-gorges reservoir area. The important regions are Changshou, Shizhu, Wulong, Jiangjin, Fengdu, Badong, Yichang, Xingshan and Banan.Finally, the study used daily weather data,land use,soil,DEM etc of Donghe basin the upper reaches of Xiaojiang River,July and September much NO3 of surfase runoff, April,July,August and September much organic N load in units area of Donghe basin agricultural filed, after simulated by SWAT model. Outcome Validated and parameter calibrated,SWAT model condition extend all Changjiang River basin′s agricultural filed.