Study on Water and Nitrogen Cycle in Jurong Reservoir Catchment

The annual nitrogen budget, the annual organic nitrogen output intensity and nitrate nitrogen output intensity from the different land use and land cover types, and the distribution law of the organic and nitrate nitrogen loss in a year along with the runoff in the Jurong Reservoir catchment are studied. By analyzing the data of N related agricultural activities through the household interviews method, the nitrogen input to the catchment is estimated at 1710.881×10³ kg N year^-1, including that from chemical fertilizer, human and livestock excreta, biological nitrogen fixation, seed nitrogen input and atmospheric deposition. The nitrogen input to the catchment via chemical fertilizer is estimated at 1253.440×10³ kg N year^-1 and it is far higher than that from the other approaches. SWAT model is used to simulate the organic nitrogen and nitrate nitrogen loss per month along with the runoff in the catchment. The annual organic nitrogen and nitrate nitrogen output intensity on the different land use and land cover types from 2005 to 2007 are calculated. The results show that the organic nitrogen output intensity on the different land use and land cover types are 19.94 kg hm^-2 year^-1 from the dry farmland, 15.65 kg hm^-2 year^-1 from the residential area and roads,10.21 kg hm^-2 year^-1 from the paddy field, 4.69 kg hm^-2 year^-1 from the tea gardens and artificial forest, and 1.95 kg hm^-2 year^-1 from the water area, in a descending order. The nitrate nitrogen from dry farmland is 0.93 kg hm^-2 year^-1, which is more than that from the land with others. With analyzing of the annual organic nitrogen and nitrate nitrogen output, it is found that the nitrogen losses are concentrated in the rainy season period.