【作者】 黄炜；

【导师】 任拥政；

【作者基本信息】 华中科技大学 ， 土木水利（专业学位）， 2022， 硕士

【摘要】 近年来随着点源污染的逐步控制,非点源污染已成为影响流域水生态与水环境安全的重要因素。本文以汉江一级支流—竹皮河作为研究对象,在水质评价和污染源调查的基础上构建了竹皮河流域的SWAT模型,进而对不同典型水文年非点源污染时空分布特征与下垫面影响因素进行了分析,筛选出了流域非点源污染的关键源区,并从环境效益和综合效益两方面选择出流域的最佳管理措施,为竹皮河流域非点源污染的防控和治理提供数据支持和理论支撑。主要研究内容及成果如下:(1)采用单因子评价法和内梅罗污染指数法对流域内8个水质断面进行水质评价,识别出氨氮和总磷为竹皮河流域的主要污染因子,竹皮河城区段和中下游石牌镇农田地区为重点污染区域。利用统计法和输出系数法对污染源进行统计调查,确定流域COD、氨氮和总磷排放量分别为3479.04 t/a、308.76 t/a和75.38 t/a,流域非点源污染占比较大,其中最大的为农田径流污染。(2)基于相关资料构建了竹皮河流域的SWAT模型,将竹皮河流域划分为33个子流域和341个水文响应单元。采用SWAT-CUP软件对模型进行校准,通过敏感性分析分别筛选出15个与径流和氮磷相关的敏感参数,并依次对径流、氨氮和总磷进行率定验证,结果均符合R~2≥0.6和NSE≥0.5,说明模型满足精度要求。(3)对不同典型水文年下非点源污染时空分布特征进行分析,发现竹皮河流域氮磷负荷在丰水年最高、平水年次之,枯水年最低,且负荷流失主要集中在每年的丰水期(6～8月),降雨量是非点源污染产生与迁移的主要驱动力。不同水文年下氮磷流失强度虽然有所变化,但空间分布特征基本一致,主要集中在荆门市主城区和石牌镇农田地区。竹皮河流域氮流失的主要形态为有机氮,磷流失的主要形态为矿物磷。(4)采用单位面积负荷指数法进行流域污染关键源区的识别,综合分析确定流域污染的关键源区为2、4、9、17、24、25、29和32号子流域,8个子流域面积占总流域面积的41.9%,总氮和总磷的贡献率分别达到62.3%和61.9%。基于关键源区识别结果,设置15种不同情景方案进行模拟,对不同BMPs的环境效益和综合效益进行评估。评估结果显示,竹皮河流域非点源污染负荷削减效率最高的是10 km长植草水道,总氮和总磷的削减率分别为21.53%和25.93%,而1 km长植草水道CE值最高,综合效益最好。说明植草水道不但对氮磷的污染负荷有较好的削减效果,而且投入成本也远低于其它措施,较为适合应于竹皮河流域。更多还原

【Abstract】 In recent years,with the gradual control of point source pollution,non-point source pollution has become an important factor affecting the water ecology and water environment security of watershed.Taking Zhupi River,a tributary of the Han River,as the research object,the SWAT model of Zhupi River basin was constructed based on water quality assessment and pollution source investigation.Then,the spatio-temporal distribution characteristics of non-point source pollution and the influencing factors of underlying surface in different typical hydrological years were analyzed,and the key sources of non-point source pollution in the basin were screened out.The best management measures were selected from the environmental benefits and comprehensive benefits to provide data support and theoretical support for the prevention and control of non-point source pollution in zhupi River basin.The main research contents and achievements are as follows:(1)The single-factor evaluation method and nemero pollution index method were used to evaluate the water quality of 8 water quality sections in the zhupi River basin.Ammonia nitrogen and total phosphorus were identified as the main pollution factors in the Zhupi River basin,and the urban section of zhupi River and the farmland area of Shipai Town in the middle and lower reaches were identified as the key pollution areas.Statistical method and output coefficient method were used to investigate the pollution sources,and it was determined that the COD,ammonia nitrogen and total phosphorus emissions were 3479.04t/a,308.76 t/a and 75.38 t/a,respectively.Non-point source pollution accounted for a large proportion of the basin,among which the largest pollution was farmland runoff.(2)Based on relevant data,the SWAT model of Zhupi River basin was constructed,and the Zhupi River basin was divided into 33 sub-basins and 341 hydrological response units.SWAT-CUP software was used to calibrate the model,and 15 sensitive parameters related to runoff and nitrogen and phosphorus were screened out through sensitivity analysis,and runoff,ammonia nitrogen and total phosphorus were calibrated in turn.The results were R~2≥0.6 and NSE≥0.5,indicating that the model met the accuracy requirements.(3)The spatial and temporal distribution characteristics of non-point source pollution in different typical hydrological years were analyzed.It was found that the nitrogen and phosphorus load in zhupi River basin was the highest in wet years,followed by normal years,and the lowest in dry years.The load loss was mainly concentrated in the wet season(June to August),and rainfall was the main driving force of non-point source pollution generation and migration.Although the intensity of nitrogen and phosphorus loss varied in different hydrological years,its spatial distribution characteristics were basically the same,mainly concentrated in the main urban area of Jingmen city and the farmland area of Shipai Town.The main form of nitrogen loss in Zhupi River basin is organic nitrogen and mineral phosphorus.(4)The key pollution source areas of the basin were identified by unit area load index method,and the key pollution source areas were identified as sub-basins 2,4,9,17,24,25,29 and 32 by comprehensive analysis.The area of eight sub-basins accounted for 41.9%of the total basin area,and the contribution rates of total nitrogen and total phosphorus were62.3%and 61.9%,respectively.Based on the identification results of key source areas,15different scenarios were set up to simulate and evaluate the environmental benefits and comprehensive benefits of different BMPs.The assessment results showed that the 10-km grass-planting waterway had the highest non-point source pollution load reduction efficiency,and the reduction rates of total nitrogen and total phosphorus were 21.53%and25.93%,respectively,while the 1-km grass-planting waterway had the highest CE value and the best comprehensive benefit.The results showed that the grass-planting channel not only had a good effect on reducing the nitrogen and phosphorus pollution load,but also had a much lower input cost than other measures,so it was suitable for zhupi River basin.更多还原