Assessing Uncertainty Of BMPs Effectiveness In Shanmei Reservoir Watershed

The rapid development of human society and economy has led to an increase in production and living water,resulting in an increasingly scarce water resource and a growing pollution of water environment.In addition,with the global climate change,the frequency and intensity of extreme disasters continue to increase,leading to more prominent problems in regional water resources and water pollution.Best Management Practices(BMPs)are one of the most effective means of managing water pollution.Combining hydrological models to analyze the effectiveness of BMPs has the advantages of short time-consuming and flexible,and is an important means for current non-point source pollution control and auxiliary watershed management decision-making in river basins.However,the parameters,structure and data input of the hydrological model are uncertain,which leads to uncertainty in the validity analysis of the BMP in the basin.At the same time,the prediction of future climate change is uncertain,and the validity and uncertainty of the lower bone morphogenetic protein under climate change can be fully analyzed,which will help to formulate more effective prevention measures and prevent the risk of water quality change under climate change.The Shanmei Reservoir Basin is located in the northwestern part of Quanzhou City,Fujian Province.It is responsible for the living and production water of the downstream population of 6 million.The annual water supply is about 1 billion m~3.In recent years,the non-point source pollution in the basin has been prominent,the total nitrogen in the reservoir area has continued to exceed the standard,and the water quality of the water source has been seriously threatened.The control of total nitrogen output in the Shanmei Reservoir Basin has become the focus of water quality management in Shanmei Reservoir.In this paper,the Shanmei Reservoir Basin is used as the study area to construct the AnnAGNPS model with high precision of the daily scale nitrogen pollution in the Shanmei Reservoir.Six kinds of BMPs were set up by scenario simulation technology,and the reduction effect of BMP on sediment and total nitrogen was analyzed.Combined with the selection of Latin hypercube sampling and the parameter selection of"parameters",the evaluation parameters were not at different time and space scales.The impact of certainty on the effectiveness of BMPs.Finally,the effectiveness and resilient of BMPs under future climate change are analyzed in combination with five GCM models and four RCP scenarios.The results showed that:(1)Under the current climatic conditions,the rate of sediment reduction in no-tillage and terraced fields was the most significant,followed by riverside buffer zone,less tillage and returning farmland to forest;the total nitrogen reduction rate of terraced fields and returning farmland to forests was the most significant.Secondly,no-till,less tillage,proper fertilization and riverside buffer zone.(2)The trend of total nitrogen reduction of BMPs in riverside buffer zone,less tillage,no-tillage,terraced fields and so on in different months is consistent with the trend of sedimentation.Rational fertilization and returning farmland to forests are more relevant to watershed fertilization..(3)There is no significant difference in the uncertainty of the load per unit area of sediment or total nitrogen in different BMPs,and the uncertainty of the unit load per unit area of sediment is greater than the uncertainty of total nitrogen.The uncertainty of sediment rate or total nitrogen reduction rate of different BMPs is different,and the difference of uncertainty of total nitrogen reduction rate is more significant.(4)On the monthly time scale,except for less tillage,the uncertainty of sediment reduction and total nitrogen reduction of other BMPs is higher than that of non-flooding period;the uncertainty of sediment reduction in each month is higher than that.Total nitrogen,in which the riparian buffer zone,the less tillage and no-till measures,the sediment and total nitrogen reduction trends are consistent.On the spatial scale,the spatial distribution of uncertainty in sediments or total nitrogen reductions of BMPs is similar,but the uncertainty of sediment and total nitrogen reduction has obvious spatial differences.(5)Under the future climatic conditions,the amount of sediment and total nitrogen reduction in no-tillage,terraced fields and returning farmland to forests is higher than that of riverside buffer belts and less tillage.The amount of BMPs sediment reduction is less affected by the GCM model and the RCP scenario.The total nitrogen reduction of less tillage and no-till is more affected by the GCM model and the RCP scenario.(6)Compared with the current climatic conditions,in the future climatic conditions,the amount of sediment and total nitrogen reduction in the riverside buffer zone is the most significant,and the total nitrogen reduction is more increased;the total nitrogen reduction of the appropriate amount of fertilization is reduced.The most significant;less tillage and no-tillage,the amount of sediment reduction is weakened,the total nitrogen reduction is increased,but the change in the amount of less tillage and total nitrogen reduction is smaller than that of no-tillage;the sedimentation of returning farmland to forests and terraces,total The amount of nitrogen reduction is reduced,but the effect of reducing the reduction of terraced sediment is basically the same as the current one.The sediment and total nitrogen reduction resilient of BMPs is affected by RCP and GCM,and is affected by GCM more than RCP.In addition,the resilient of total nitrogen reduction is more affected by GCM and RCP than sediment.