Study on Agricultural Non-Point Source Pollution Load of Typical Facility Farmland in the Downstream of the North Canal River Watershed

Generally,rainfall-runoff is thought to be the major impetus leading to the export of nonpoint source pollutants.Based on the preliminary studies on loss of pollutants from facility farmlands,rainfall-runoff and irrigation are two major driving factors leading to non-point source pollution from facility farmlands. To quantitatively investigate non-point source pollution load of the facility farmlands in the downstream of the North Canal,the Beichen Shuangjie Greenhouse Grape Demonstration Park was cited as object of the study. Analysis of the models for rainfall-runoff pollution load (SCS,USLE,adsorbed nitrogen and phosphorus pollution loads and dissolved N and P pollution loads) and the model for irrigation pollution load (model with modified export coefficient) was done and modification of the models made. Then the modified models were used to simulate and analyze run-off and irrigation processes for assessment of pollution load from the park. Results show that the export load of adsorbed nitrogen and phosphorus from the park reached 40. 98 and 1. 42 kg·a^-1,respectively,in the rainy season,while the load of dissolved ones was 628. 77 and 4. 57 kg·a^{- 1,}respectively; the load of total nitrogen,total phosphorus,ammonium nitrogen and nitrate nitrogen during the irrigation period was 182. 15,2. 56,60. 49 and 62. 82 kg · a^-1,respectively. The study demonstrates that the modified models are good in simulation and worth further extrapolating.