Spatial And Temporal Variations Of Agricultural Non-Point Source Pollutant Loads And Water Resource Security Level In The Three Gorges Reservoir Area Of Chongqing

Agricultural non-point source pollution(NPSP) is becoming an increasingly important eco-environmental problem;It has become the major source of river basin pollution in China, it is difficult to control due to its dispersive and extensive characteristics. The Three Gorges Reservoir area is typical frangible ecotope. Therefore,water resource security is especially important.After the impact of the Three Gorges Reservoir impoundment of water quality has become a domestic and international experts to study the topic.After the Three Gorges Reservoir, the river’s flow regime, the physical and chemical conditions have changed.As a result, the impact of agricultural non-point source pollution of water due to environmental safety basin gradually emerge.According to the investigation on the pollution sources of chemical fertilizer, organic manure, Crops straw, breeding, aquiculture, dormitory sewage, dormitory wastes and soil erosion in the Three Gorges Reservoir Area(TGRA) of Chongqing, the Arc GIS software was adopted to analyze the spatial and digital features of agricultural non-point source pollution. Spatial and temporal variations of the absolute discharge amount of NPSP in the TGRA of Chongqing were analyzed at the districts(counties) level using the spatial cluster and hot and cold spots analysis methods.Spatial and Temporal Variations of water resource security level was analyzed by using geostatistical methods and Nemerow index based on theoretical data and monitoring data at the districts(counties) level.There were three major findings from the study.(1)The results showed that the absolute discharge amounts of COD,BOD5, TN, TP from NPSP were 15.85, 7.35, 5.50 and 0.97 thousand ton per ye ar in 2005.The absolute discharge amounts of COD,BOD5, TN, TP from NPSP were 10.93, 6.45, 5.60 and 1.04 thousand ton per year in 2008.The absolute discharge amounts of COD,BOD5, TN, TP from NPSP were 14.67, 8.68, 6.94 and 1.14 thousand ton per year in 2011. The absolute discharge amount of COD、BOD5 experienced a trend of rose after the first drop, but the absolute discharge amount of TN 、TP always showed an upward trend from 2005 to 2011.(2) Moran’s Index values remained high from 2005 to 2011(although with a downward trend in2008).(3) Judging from the results of the hot and cold spots analysis, the hinterland of the Three Gorges Reservoir area(Chongqing section) was the hotspots, whereas the metropolis’ core district of the end of the Three Gorges Reservoir area(Chongqing section) was the cold spots. The primary contaminated districts(counties) were Yunyang, Wanzhou, Kaixian, which are all located in the hinterland of the TRGA(Chongqing section). The study provided scientific basis for the evaluation of NPSP in Chongqing.(4) From the judging the absolute discharge amounts of COD,BOD5, TN, TP in equivalent standard,the main pollutants of NPSP in the TGRA of Chongqing is TN, TP.(5) Judging from the results of the spatial and temporal variations analysis of the relative absolute discharge amount of pollutants, the primary contaminated districts(counties) were Dadukou and Jiangbei. The relative absolute discharge amount of pollutants in equivalent standard on lang area in the TGRA of Chongqing increased from 3.21t·km-1 to 3.23t·km-1.(6) From the judging the amount of water quality concentration in 2005、2008、2011 in the TGRA of Chongqing,the concentration of TN, TP had exceeded the Surface Water Quality Standards III.(7) The results showed that the Nemerow index of theoretical data were 2.48,2.51 and 2.88 in 2005,2008 and 2011. Judging from the results of the spatial and temporal variations analysis of Nemerow index(theoretical data), with the completion of the reservoir water, the water resource security level of the hinterland and central of the TGRA(Chongqing section) has declined,whereas the metropolis’ core district of the end of the TGRA(Chongqing section) has improved.(8)The Nemerow index of monitoring data were 1.26,1.38 and 2.14 in 2005,2008 and 2011. The results of theoretical data and monitoring data showed tha tthere was similarity in the spatial distribution.(9)The high coincidence was showed by comparing of the monitoring data and theoretical data in the TGRA of Chongqing.