Attribution Analysis Of Runoff Changes And Research Of Soil & Water Conservation BMPs In Yiluo River Basin

Yiluo River Basin is the wettest area in the middle reaches of the Yellow River,and it is an important river to support the economic development of Henan Province.In the past 40 years,climate change and human activities have greatly influenced the hydrological balance of the Yiluo River Basin.And,global warming may increase precipitation,soil erosion,especially in the upper reaches of Luohe River.It will threaten the service life of the Guxian Reservoir in the lower reaches.This study,based on the SWAT model,quantitatively evaluated the impact of climate change and human activities on the hydrological components,and,the capability of soil & water conservation best management practices(BMPs)in Yiluo River Basin.The specific research results are as follows:(1)The result showed that the change of HRUs quantity has little effect on runoff simulation.The time of calibration reduced 20.5%-3.8% because of the setting range of HRUs threshold with the value 5%-10%.Multi-objective calibration based on NSGA-? obtain a satisfactory NSE value which is similar to PSO algorithm,while PBIAS value is reduced by 3.7%.This means that NSGA-? algorithm can constrain the model calibration process from both two aspects(trend and error),thus reducing the model uncertainty.(2)In the study,1976-1985 was set as the baseline period(S1).1986-1995,1996-2005,2006-2015 were set as the influence period and named S2,S3 and S4,respectively.The results showed that in S2 and S4,the impact of climate change on runoff change is greater than that of human activities,while in S3,it is less than that of human activities.The relative contribution rates of S1,S2 and S3 caused by climate changes are 72.2%,46.3% and 86.8%,respectively.Human activities are further divided into the effect of land use/land cover change(LUCC)and he effect of water resource utilization behavior and policy(WRUBAP).The results show that the impact of human activities on runoff in Yiluo River Basin is mainly caused by WRUBAP,while the impact of LUCC is less.(3)in the mountainous area of the upper reaches of Luohe River Basin(the control hydrological station is Lingkou station),afforestation can increase the groundwater and surface water volume,reduce the actual evapotranspiration and maintain it at an annual average of about 590 mm.The influence of filter and terracing on hydrological components is small.As far as the effect of sediment reduction is concerned,afforestation has the best effect,and even the proportion of sediment yield decrease more than 90%.In addition,when the filter is applied in the soil erosion hotspots of grassland,the proportion of sediment yield decrease can be maintained over 30%.However,when the filter is individually applied in the soil erosion hotspots of farmland,the effect of sediment reduction is weakness.