Analysis On Water And Soil Conservation And Non-point Source Pollution Of Hill-Type Villages And Towns

As hill-type township adjacented to stream in the upper reaches of Tiaoxi River, pollutantswhich were carried by rainfall runoff into the river caused serious harm to the river waterenvironment. With the decelopment of urbanization, surface runoff of small towns became thekey pollutions output areas. Therefore, to study runoff pollution characteristics of typiclhill-type villages and towns surface, researching and developing targeted pollution controltechnology and conducting engineering demonstration is important and has a popular value.This study selected Senzhuyuan Basin and Hongdu village in Lin’an City as the researchobject, planned and designed Senzhuyuan Basin non-point source pollution control engineering,carried out non-point source pollution control demonstration project. According to the problemof soil erosion in slope, ecological slope protection greening restoration and experimental studywere conducted, and non-point source pollution law of Senzhuyuan Basin was studyed based oncontinuous natural rainfall condition. As year pollution load is hard to research in natural rainfallcondition, we selected Hongdu village as the research object to conduct artificial rainfallsimulation ecperiment to study the pollutant losing law and estimat non-point source pollutionload. The purpose is to create a healthy upstream river ecosystem, controlling eutrophication ofQingshan Reservoir, to improve the water quality flow to middle reaches of Tiaoxi River, toprovide scientific and technological support on water environment governance. The main resultswere as follows:1) Non-point source pollution control engineering was been conducted based on the overallinvestigation of Senzhuyuan Basin. The major project include: roof rainwater purification andutilization engineering, rain retention pond—purification pool engineering, mountain rainpurification and utilization engineering, hillside repair and green engineering, ground rain waterpurification infiltration engineering and ecological stable pool. According to the design scheme,the Senzhuyuan Basin was be constructed and repaired to achieve non-point source pollutionprecention effect.2) Researching vegetation growth status of the ecological slope, monitoring the soilmoisture condition and observing vegetation growth status at the same time, the best soil watercondition and plant species which had the soil and water conservation effect were elected. There were30%~40%, tall fescue and bermudagrass respectively. Comprehensive comparison analysiswere conducted in suspended net spray-sowing ecological slope protection technology andecological bag slope protection technology through soil moisture, vegetation growth status,construction progress, slope stability, cost and comprehensive benefit aspects. The resultsshowed that cost of suspended net spray-sowing technology is low and construction progress isfast, but the ecological bag technique is better in the slope stability and comprehensive benefitaspect.3) The area of Senzhuyuan Basin is118797.52m2. research on non-point source pollutionlaw in48hours continuous rain condition showed that:①The average values of TN、TP、COD、NH3-N concentration of rain were0.085mg/L、0.034mg/L、1.569mg/L、0.023mg/Lrespectively. During rainfall propess the ecological pond accepted the total amount of fourcontaminants from rain were as follows respectively:20.96g、8.38g、386.82g、5.67g. Thewhole basin accepted the total amount of four contaminants from rain were as followsrespectively:1234.89g、493.96g、22794.59g、33415g. According to the surface waterenvironment quality standard (GB3838-2002) can be seen, the average values of TN、COD、NH3-N concentration of rain belonged to class Ⅰwater, TP concentration belonged to class Ⅱstandard. The overall water quality is good. As the storm lasted for a long time, the intensity andtotal amount of rainfall is large, the total amount of accumulation of rain water pollutants in thewhole rainfall process is a little more.②The entire watershed discharged the amount of TN、TP、COD、NH3-N pollutants to the downstream were7389.643g、2271.054g、394058.5g、1212.477g respectively.③Among the non-point source pollution control demonstrationprojects, the stable ecological pond played an important role in controling non-point sourcepollution. The reduction of TN、TP、NH3-N and SS were13399.3g、3576.71g、1124.033g、595004.5g respectively, and the reduction rate were about64.45%、61.16%、48.11%、100%respectively. As there were aquatic purify plants and a few species in the ecological pond, CODincreased slightly and the amplitude was about15.6%.4) Take the Hongdu village as the research object, considering the different land use types,choosing different rainfall intensity, the contaminants output characteristics were analyzed andrainfall runoff concentration were obtained based on artificial rainfall simulation experiment.The runoff coefficient estimation of different land types were also obtained by the equation SCS, and the pollution load per year of Hongdu village were estimated by using pollution loadcalculation formula. The results showed that the non-point source pollution output loads ofTN、NH3-N、TP and COD in Hongdu Village were4037.31、1834.68、337.88and31833.06kg/a respectively. Because of the large area of forest in this region,T N、NH3-N、TP and CODis a little high,which showed the result2369.52、1028.55、182.32和19862.69kg/a.