Analysis And Spatio-temporal Distribution Of Pollution Loading In Hubei Section Of Three Gorges Reservoir Area

Adverse impacts of Three Gorges Projects on ecological-environmental systems have always been the focus point of studies home and abroad. In recent decades, as the development of society and economy in Three Gorges Reservoir Area (TGRA) and its upper reaches, the construction of city is very fast and the sewage come from industry and town living increase continuously, the chemical fertilizer is used more widely and frequently, along with serious water and soil loss. The pollution of water quality in Three Gorges Reservoir is more and more critical.In this study, the pollution source loads in Hubei section of TGRA were investigated and analyzed to learn the rule of time change and spatial distribution of the pollution source loading to provide scientific principles for the water resources controlling plans and the decisions of treating eutrophic watersheds. This system study has significances to environmental protection for local region and our country. The main researeh contents and results of this paper are ineluded asfollowing:(1) By using Grey Model-Markov chain model, the amount of industrial wastewater and COD in Hubei region of TGRA are predicted from2010to2020. And the populations of each area in Hubei region of TGRA are predicted by using Grey Model, combining with emission coefficient method to estimate the quantity of urban life pollution loading to provide advices for local environmental protection department. The results indicate that the amount of industrial wastewater presented a rising trend while the emission amount of COD presented a declining trend after2009. The main pollutants of sewage like COD, NH3-N, TN and TP from urban life source changed little in Hubei region of TGRA in the next decade.(2) The export coefficient model was used to calculate the Non-point Source loading to Hubei region of TGRA. Despite its limitations, export coefficient model provided a simple tool for forecasting, in terms of N and P loading, the impact of future rural development planned for Hubei region of TGRA. The results indicate that the main pollutants like COD, TN and TP from rural domestic wastes presented a declining trend, the pollutants from distributed livestock farms changed little except rising in2009, the TP load from land use changed little while the TN load began to generally decrease since1999, the TN and TP loads from runfall changed along with rainfall from1995to2009.(3) The impact of main pollution area, main pollution source and main pollutant in Hubei region of TGRA were evaluated by using Equivalent standard pollution index method. The results indicate that according to the pollution stress, spatial distribution of the pollution source loading was Yiling District> Badong County> Zigui County> Xingshan County, and according to the pollution source, Land use> distributed livestock farms> rural domestic wastes≈urban life wastewater> rainfall> industrial wastewater, then according to the pollutants, TN> TP> COD.(4) After the impoundment of the Three Gorges Reservoir since June of2003, the water qualities of its tributaries have been influenced. The ratios of potential TN/TP loads were above13.50before2003except1997. Then they were under13.50in the following7years. On the other hand, the "algae blooms" occurred every spring and summer in some tributaries of Three Gorges Reservior and even in the water area in front of the Three Gorges Dam after2004, and it becomes more and more serious year by year. The driving forces of temporal-spatial changing of pollution sources in the study area mainly come from natural factor (i.e. landform, climate, soil, etc.) and social economic factor (i.e. population growth, economic situation, etc.). Additionally, effect of the impoundment of Three Gorges Project should not been ignored.