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由于化肥、农药的过量施用，加之传统的淹灌稻田排水量大，导致随稻田排水流失的污染物量大，加剧了农田面源污染，因此，在农田排水的设计中不仅要控制涝渍危害，也要控制排水中的水质，以减轻对下游及承泄区造成的污染。以湖北省襄阳老河口市仙人渡镇的新增粮食生产能力项目区为对象，以生态排水沟和人工湿地作为稻田排水水质处理的手段，以总氮作为排水水质控制指标，建立了生态排水沟和人工湿地的水质模拟模型，选定不同的生态沟和人工湿地的组合方案进行了水质模拟。结果表明，采用生态沟和人工湿地共同作用的排水系统在满足传统除涝排渍要求的条件下，可以有效地削减稻田排水中的总氮；人工湿地布置在干沟出口时的水质净化效果最好。采用“等效替代法”计算了生态沟和现有湿地、新建人工湿地的对水质净化效果的等效性，结果表明，就处理水质的效果而言，当水平投影面积相同时，干沟出口的湿地效果最好，其次是与排水沟相连的现有湿地，最后是排水沟，三者的面积等效比为 1：8.4：938.5；优选方案中生态沟和现有湿地、新建人工湿地对水质净化的贡献率分别为 2.9%、30.3%和 66.8%。模拟结果还表明，生态排水沟的纵坡、糙率在设计范围内（坡度在 1/2 000~1/5 000 之间、糙率在 0.025~0.04 之间）变化时，对于水质处理效果几乎没有影响。
Due to the excessive application of chemical fertilizers and pesticides, combined with the large displacement of traditional flooded paddy fields, the amount of pollutants drained by the paddy field is large and the non-point source pollution of farmland is exacerbated. Therefore, not only the waterlogging hazard should be controlled in the design of farmland drainage, To control the water quality in the drainage, to reduce the pollution caused by downstream and discharge areas. Taking the newly-increased grain production capacity project area in Xianrendu, Laohekou, Yangyang, Hubei as an object, taking ecological gutters and constructed wetlands as the means of water quality treatment of paddy field drainage, and using total nitrogen as drainage water quality control index, an ecological drainage ditch And artificial wetland water quality simulation model, selected different combinations of ecological ditch and constructed wetland water quality simulation. The results showed that the drainage system with ecological ditch and constructed wetland can effectively reduce the total nitrogen in the drainage of rice paddy under the condition of meeting the requirements of traditional waterlogging and drainage, and the water purification effect when the constructed wetland was arranged at the outlet of ditch it is good. Equivalent substitution method was used to calculate the equivalence of ecological ditch and existing wetland and newly built constructed wetland to water purification effect. The results showed that when the horizontal projection area was the same, the dry ditch outlet Of the wetland is the best, followed by the existing wetland connected with the drainage ditch, and finally the drainage ditch, the area equivalent ratio of the three is 1: 8.4: 938.5; the optimal scheme of the ecological ditch and the existing wetland and the new constructed wetland The contribution rate of water purification was 2.9%, 30.3% and 66.8% respectively. The simulation results also show that when the vertical slope and roughness of the ecological drainage ditch are within the design range (the slope is between 1/2 000 ~ 1/5 000 and the roughness is between 0.025 ~ 0.04), the water treatment effect almost No effect.