Research On The Influence Of Main Function Oriention On Non-point Source Pollution In Typical Functional Zones In The Interval Basins Of The Three Gorges Reservoir

The impoundment operation of the Three Gorges Project not only brings great economic benefits,but also significantly changes the original topography and geomorphology,hydrological regime of the Three Gorges Basin（TGB）.The changes of landscape pattern and ecological environment in the basin has been accelerated since the implementation of the main function region strategy,making Non-point source（NPS）pollution problem more complex of the TGB.In the historical context of strengthening ecological and environmental protection,striving to pollution prevention and control,and Promoting ecological civilization construction,it is of great importance to study the influence of land use change on NPS pollution in Typical Functional Areas of the TGB,which is essential for non-point pollution source control and the unification of ecological civilization construction and main function region construction of the TGB,and playing a key background role for promoting modernization featuring harmonious development between man and nature.Based on the comprehensive consideration of the main functional oriention and spatial distribution characteristics of each region and county in the TGB,this paper selects Xingshan County,the key ecological functional zone under the jurisdiction of Xiangxi River Basin in the upper reaches of the Three Gorges,and Kaizhou District,the key development zone under the jurisdiction of Pengxi River Basin in the middle reaches as the study area.On the basis of distributed physical model,the non-point source models of Xiangxi River Basin and Pengxi River Basin were constructed and calibrated.Then the change trend of land use,total nitrogen（TN）pollution load and total phosphorus（TP）pollution load of non-point source pollution in Xingshan County and Kaizhou District under different functional orientation,were analyzed based on the simulation results of non-point source model.The main research contents and findings include:（1）Aiming at the impact of the construction of main functional areas on the regional environment,a set of technical methods for quantitatively evaluating the impact of different principal functional locations on land use and non-point source pollution load in districts and counties is put forward and and applied in the two typical main functional areas of Xingshan County,key ecological function zone and Kaizhou District,key development zone.（2）Based on distributed physical model and high precision DEM,meteorological and hydrological,soil and additional non-point source data at Township scale,non-point source pollution models in Xiangxi River Basin and Pengxi River Basin were constructed and the model parameters were calibrated and validated by measured runoff and water quality data.A acceptable simulation was got that the R²≥0.71 and E_NS≥0.60,which proved that the model had good simulation effect and met the requirement of simulation accuracy in research area.（3）The changes of land use before and after the implementation of the main functional zoning strategic system in the two typical main functional areas of Xingshan County,key ecological function zone and Kaizhou District,key development zone were analyzed.Different functional orientions have different impacts on land use change in Xingshan County and Kaizhou District.The location of key ecological functional zone has accelerated the average annual increase of forest land area and the average annual reduction rate of cultivated land and grassland area in Xingshan County,and delayed the average annual expansion rate of construction land area.The oriention of key development zone delayed the increase of forest area and the reduction of cultivated land area in Kaizhou,accelerated the reduction of grassland area and the expansion of construction land area.From 2005 to 2015,the area of forest land,water area and construction land in key ecological function zone Xingshan County and key development zone Kaizhou District,increased,while the area of cultivated land and grassland decreased.After the implementation of the main functional zoning strategy system in 2010,the annual average growth rate of the forest land in Xingshan County,under the key ecological function zone oriention,and the annual average reduction rate of cultivated land and grassland area increased from 2.2%,5.4%and 1.4%to 2.7%,10.6%and 1.5%respectively,with the annual average growth rate of construction land area decreasing from 11.1%to 3.4%.Moreover,the annual average growth rate of the forest area,in the Kaizhou District,under the key development zone oriention,and the annual average reduction rate of the cultivated area decreasing from 9.7%and 9.4%to 5.3%and 8.3%respectively.And the annual average rate of decline in grassland area and the annual average rate of increase in construction land increased from 1.4%and 5.3%to 11.0%and 29.9%,respectively.（4）The changes of TN and TP pollution loads of NPS before and after the implementation of the strategic system of main function zoning in two typical main functional areas of Xingshan County,key ecological function zone and Kaizhou District,key development zone wer,were studied.Different functional orientions have different effects on the pollution load of non-point source TN and TP in Xingshan County and Kaizhou District.The oriention of the key ecological functional zone increased the annual average reduction rate of TN and TP pollution loads in Xingshan County,while the oriention of key development zones reducing the annual average reduction rate of non-point source TN and TP pollution loads in Kaizhou.From 2005 to 2015,the load of TN and TP in the key ecological function zone Xingshan County and the key development zone Kaizhou District,showed a downward trend.The total load of TN in Xingshan County and Kaizhou District decreased by 1395t and927t respectively,while the TP load decreased by 77t and 171t respectively.After the implementation of the main functional zoning strategy system in 2010,the annual average reduction rates of TN and TP pollution loads in Xingshan County under the key ecological functional oriention were increased from 7.8%and 9.1%to 8.0%and 9.6%,respectively.While,the annual average reduction rates of TN and TP pollution loads in the Kaizhou area under the key development zone were reduced from 3.6%and 5.1%to 1.0%and 1.5%respectively.（5）Aiming at the change of main functional zone,the law change of TN and TP pollution loads in Xingshan County and Kaizhou District under different main functional oriention was simulated and analyzed.Compared with before the implementation of the strategy of main functional areas in 2010,the TN and TP loads in Xingshan County and Kaizhou District increased under the orientation of main agricultural production zone.While the TN and TP loads in Xingshan County and Kaizhou District decreased under the orientation of key development zone and key ecological functional zone,but the reduction rates were different.The reduction rate of TN and TP loads in Xingshan County and Kaizhou District under the oriention of key ecological functional zone was higher than that under the location of key development zone.