Study On Characteristics Of Non-point Source Pollution In Haoping River Watershed Of Danjiangkou Reservoir Distinct

In this paper, the characteristics of non-point source pollution in different slopes and land uses were studied in Haoping river watershed,which is a tributary of Laoguan river—the largest tributary of Danjiangkou Reservoir in Henan. 15 runoff ponds of five groups were built, and the rain, runoff and water quality were monitored. The results showed that:(1)the distribution of annual precipitation in Haoping watershed was variable, and the centralized storm rainfall was the main type generating non-point source pollution.(2)The average runoff coefficients of 0～5°, 5～10°, 10～15°cropland, oak forest and garden were 2.01%, 2.98%, 5.44%, 16.47% and 2.42% respectively. When rainfall erosivity (R) was greater than 0.5, oak forest in the steep slope began to generate runoff, and the main type was infliration excess runoff. When R was greater than 2.5, garden started to generate runoff, and the main type was saturation excess runoff.Cropland was dramatically affected by human, so it was not easy to determine the runoff boudary, and the main type was saturation excess runoff in centralized storm rainfall. The product of runoff and R showed a linear correlation in the oak forest(R2=0.939) and the garden(R2=0.912). The runoff and rainfall erosivity had no significant correlation in cropland, because it was significantly affected by human. In the condition of centralized storm rainfall, runoff was mainly affected by slope. The product of runoff in the cropland had significant difference between 0～5°, 5～10°and 10-15°cropland(P<0.05). In the condition of centralizd light rain, soil crust was the main factor affecting runoff.(3)The loss of nitrogen, whose main source was excessive application of fertilizer, was dominated by dissolved nitrogen, while the loss of phosphorus, whose main source was soil erosion, dominated by particulate phosphorus. Slope cropland was the major regional for generating non-point source pollution, the amount of total nitrogen loss had significant difference between 0～5°and 10-15°, 5～10°and 10-15°cropland(P<0.05) in the two previous heavy rainfalls after fertilization, and there was a significant difference between 0～5°and 5～10°cropland in extreme rainfall(R>180). In the condition of centralized storm rainfall, the amount of total phosphorus loss had significant difference between 0～5°and 10-15°, 5～10°and 10-15°cropland(P<0.05). It has a very important practical significance for implementing of terraced fields construction, taking agricultural activities to avoid heavy rain in the impaction of soil and water conservation, and reducing runoff and agricultural non-point source pollution. In addition, forest land such as oak was also important region for generating non-point source pollution, great attention should be paid.(4)In the condition of centralized storm rainfall, the amount of sediment loss had significant difference between 0～5°and 10-15°, 5～10°and 10-15°cropland(P<0.05). The sedements of different years had large difference, during the experimental period, the loss of sedements in 0～5°, 5～10°, 10～15°cropland, oak forest and garden were 142.54,191.50,1458.45,1253.31and 211.64kg/hm2 in 2008, and 6.53,7.54,15.96,99.96 and 27.49 kg/hm2 in 2009. 10～15°cropland and oak forest in steep slope are critical source area for soil erosion, great attention should be paid.(5) It has a very important practical significance for implementing of terraced fields construction, taking agricultural activities to avoid heavy rain in the impaction of soil and water conservation, and reducing runoff and agricultural non-point source pollution. In addition, forest land such as oak was also important region for generating non-point source pollution, great attention should be paid.