| The problems of soil erosion and soil erosion on slopes have become the leading factors restricting the development of agriculture and the formation of disasters.Not only are they related to agricultural production,the utilization of rivers and lakes,but also the ecological environment and economic sustainability of the entire region development of.In this experiment,by selecting five communities with different soil and water conservation measures in the Shixia small watershed,the characteristics of runoff and sediment production were analyzed under natural rainfall conditions,and the total phosphorus loss(TN),total nitrogen loss(TP),The output of the three pollution indicators of chemical oxygen demand(COD)is monitored,and the correlation analysis of runoff depth,runoff coefficient,sediment yield,TP,TN,COD and rainfall data is carried out to explore the runoff and sediment yield of different runoff communities Laws and characteristics,and select the best soil and water conservation measures,the results show that:(1)Different soil and water conservation measures have a positive effect on the control of sand and flow in the community compared with the bare land control group.The analysis shows that there is a significant linear relationship between rainfall and runoff depth;in the analysis of rainfall and runoff coefficient,except for fish scale pits and terrace measures,there is a negative correlation between runoff coefficient and rainfall in other plots,and other plots do not show correlation.In this experiment,rainfall has little effect on runoff coefficient;there is a linear function relationship between sediment yield and runoff depth.In the process of runoff reduction,the values of flow reduction rate of each community are: 33.98% for slope farmland measures,86.41% for large horizontal strip measures,79.61% for fish scale pit measures,80.58 for artificial grass planting measures,and 83.50% for terraced field measures;the process of reducing sediment output Among them,the sand reduction rate data are 52.53% for slope farmland measures,84.91% for large horizontal strip measures,93.54% for fish scale pit measures,95.77% for grass planting measures,and 97.25% for terraced field measures.In the process of occurrence,the most effective measure for reduction is the terrace measure.When the rainfall increases,it can also play a more significant reduction effect,followed by the fish scale pit measure,so these two measures should be used in consideration of actual layout,and These two measures can be based on local materials and construction,and are more in line with local development status.(2)Rainfall is the root cause of erosion and sediment production on slopes,which has a great impact on soil erosion and non-point source pollution.Therefore,the multi-year rainfall data in the study area is collected to obtain the rainfall change trend and predict the future rainfall trend.During the period from 1970 to 2015,the rainfall trend in July and August fell overall,and the rainfall decreased.The rainfall in July fluctuated greatly in 45 years,and the average rainfall in July was greater than the average rainfall in August.The trend is generally not significant;in the monitoring of interannual rainfall change,the rainfall range is 537.6 mm,and the MK analysis of the annual rainfall change trend shows a decreasing trend,and the trend is not significant;when the total rainfall in the flood season increases,except for artificial Except for grass planting measures,there is a linear relationship between the total rainfall and sediment yield of the other five measures,and the two data of the large-level measure measures are at the 0.05 level(two-tailed),and the correlation is significant;The fish scale pits,terraces and control bare land are all in the 0.01 level(two-tailed),and the correlation is significant.(3)Under different rainfall conditions,the correlation analysis of the rainfall and each pollution index of each community shows that there is a linear relationship between the output of the nitrogen pollution index and the rainfall;In measure plots,artificial grass planting and terraced measure plots,there is a linear relationship between the output of phosphorus pollution indicators and rainfall,there is no correlation between the slope farmland and the control group,and there is an exponential relationship between COD pollution indicators and rainfall;nitrogen pollution output The quantity reduction rate from strong to weak are: 90.18% in terraced measure area,83.73% in fish scale pit measure area,80.77% in large horizontal strip measure area,and 80.59% in artificial grass plantation measure area;the reduction rate of phosphorus pollution output is from strong to weak It is: 92.91% in fish scale pit measure community,92.13% in terraced measure community,87.82% in large horizontal strip measure community,and 82.24% in artificial grass planting;the reduction rate of COD for organic matter pollution index in runoff exceeds 50% in all four communities.From strong to weak,they are: terraced fields 82.3%,artificial grass planting measures 73.52%,large horizontal strip measures 58.8%,fish scale pit measures 58.47%.Based on the reduction rate of the three pollution indicators,the best measures to reduce the total output of pollutants are terraces,followed by fish scale pits,followed by large horizontal strips,and finally artificial grass planting. |
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