北江飞来峡库区典型流域非点源污染特征分析及模拟

为分析飞来峡库区典型流域非点源污染状况,开展社岗流域场次降雨径流水量水质监测试验,采用平均浓度法估算非点源污染负荷量,分析各场次降雨径流污染物特征并计算非点源污染贡献率,应用SWAT模型进行径流及非点源污染模拟。结果表明,径流量对SS、BOD_5等浓度和负荷量均有较强的主导作用,TN、NH_3-N等初期冲刷效应较为明显,污染物负荷量与径流量的相关性好于污染物浓度与径流量的相关性,各污染物的非点源污染贡献率均达到80%以上。SWAT模型径流模拟的率定期和验证期效率系数分别为0.85和0.73,表明所构建的SWAT模型精度良好。在污染物率定期,雨强较大的典型日污染物模拟效果最佳,污染物相对误差基本在10%以内,而在雨强较小时,TN、TP等均出现较大程度的低估现象;在污染物验证期,由于该时期正处于春耕施肥期,TN、TP模拟结果相对误差较大,且均为低估。总体而言,SWAT模型模拟精度良好,基本能反映该流域非点源污染状况,可为飞来峡库区流域的非点源污染模拟与控制提供参考。

Characteristic analysis and simulation of non-point source pollution in typical watershed of Feilaixia Reservoir area

In order to analyze the non-point source pollution of the typical watershed in the Feilaixia Reservoir area, an experiment of water quantity and quality monitoring in each rainfall events in Shegang watershed was conducted, and non-point source pollution load was estimated by mean concentration method, analyzing the pollutant characteristics of runoff from different rainfall events and calculating the contribution rate of non-point source pollution. Simulation of runoff and non-point source pollution was made by using SWAT model. The results show that: runoff plays a dominant role in the concentration and load of SS, BOD₅, etc. ; the initial scouring effect of TN and NH₃-N is obvious; the correlation between pollutant load and runoff is better than that between pollutant concentration and runoff; the contribution rate of non-point source pollution of pollutants is more than 80%. The efficiency coefficients of SWAT model for runoff simulation in calibration and validation periods are 0. 85 and 0. 73, respectively, showing that the SWAT model has good accuracy. In the pollutants calibration period, typical daily pollutants with strong rain have the best simulation effect, with the relative error of pollutants within 10%. When the rain intensity is low, TN and TP are underestimated to a large extent. In the pollutants validation period, since it is in the spring ploughing and fertilizing period, the relative errors of TN and TP simulation results are large and underestimated. In general, SWAT model has good simulation accuracy, which can basically reflect the non-point source pollution situation in the basin, and can provide reference for non-point source pollution simulation and control in the Feilaixia Reservoir Basin.