Research Of Nutrient Loss From Heimiaogou Watershed In Danjiang Reservoir Area Based On GIS

"South-to-North water transfer" is the major strategic project in the beginning of the21st century for China to achieve a reasonable allocation of water resources and solve thewater shortage problem in the north. Its key factor lies in the water quality. As the watersource of middle route line of South-to-North Water Transfer Project, the water quality ofDanjiang reservoir is at good situation and is suitable for water transfer in general.However, by study we found serious water pollution problems existed in some branchesof the upriver area. Most of the pollution of these rivers is caused by agriculturalnon-point-sources pollution except a little point-source pollution. In order to implementthe three "first-then" principles " issued by State Council, which is "save first, then adjust;control first, then connect; protect first, then use", is important for us to launch thenon-point source agricultural research in the reservoir area, to explore a reasonable andapplicable way to predict the hill-based agricultural non-point source pollution load of thewhole Danjiang Reservoir and to bring forward effective pollution control measures.Ensuring the effective protection of water resources and preventing the deterioration ofwater quality.Heimiaogou watershed in Danjiang reservoir area was chosen as the study object.The actuality of agriculture non-point source pollution in this area was studied based oncomprehensive investigation, we classified watershed slope unit and adopted theUniversal Soil Loss Equation (USLE) to predict the soil erosion; Meanwhile combiningthe relationship between sediment and nutrient loss in the artificial rainfall simulation inlaboratory with 12 different treatments, the load of nutrient loss was simulated by us inHeimiaogou watershed in 2005. The main conclusions are presented as fellows:(1) The average annual input of total nutrient (TN) and total phosphorus (TP) byfertilize in Heimiaogou watershed are 51.18 tons and 13.88 tons respectively; the total TNand TP which are input by Livestock fertilizing are 3.58 tons and 0.75 tons respectively;the annual amount of pesticides is about 1.35 tons; the total average amount input of TNand TP by life pollutants are 163.03 kilograms and 30.77 kilograms respectively.(2) The soil erosion of Heimiaogou watershed is 6927.86 tons in 2005; the averageannual soil erosion modulus is 3610.67t/km~2 which belongs to moderate erosion.(3) Rainfall simulation results show that the nutrient content in topsoil caused by soilerosion had decreased before and after the rainfall in the 12 experiments and the availablenutrient loss ratio is higher than that of total nutrient loss ratio in every process, especiallyavailable nitrogen is 8.69. This indicates the impact to available nutrients cased by runoff is greater than that of to the total nutrients.In every experiment, enrichment ratio of nutrient is all above 1.0, organic matter1.43, total nitrogen 1.72, total phosphorus 1.46, total potassium 1.38. The concentrationof the available nutrient is greater than the total nutrient, and available nitrogen 2.21,available phosphorus 2.64, available potassium 1.52. The nutrient enrichment ratiodecreases with the increase of the slope and rainfall intensity. Nitrogen and phosphorusfertilizer causes the increase of nitrogen and phosphorus of the treatments, except the totalphosphorus. After fertilization, the accumulation of nitrogen and phosphorus in thesurface increases, thus the sediment of nitrogen and phosphorus nutrients carried bysediment increases, but this has little impact on the loss of organic potassium nutrient.(4) The loss of nutrient in Heimiaogou watershed in 2005 is as bellows: organicmatter 36.06t, total nitrogen 3.34tons, total phosphorus 1.84tons, potassium 56.09tons,available nitrogen 0.46tons, available phosphorus 0.05tons, and available potassium0.61tons. The trends is consistent between the sediment erosion and nutrient loss, steepslope land＞ramp land＞flat land, farmland＞woodland.In the end, aiming at the feature of agriculture non-point pollution in Heimiaogouwatershed, some proposals in managing and controlling non-point source pollution havebeen put forward from "Source control-Interception-Transform" three factors.