The Impact Of Climate Change And Human Activities On The Inlet Runoff Of Koutou Reservoirs

The Koutu Reservoir is a large scale reservoir in the upper reaches of Baiyangdian,with the two important tasks of irrigation and flood control.Since the beginning of the 21st century,the incoming runoff of Koutu Reservoir has changed significantly,which has had a certain impact on the normal operation of the reservoir.Therefore,this paper uses a long series of hydro-meteorological data from 1980 to 2018 in this basin controlled by the reservoir,and establishes a distributed hydrological model of the basin based on the analysis of the changes in the inlet runoff,combined with the soil condition and land use in the basin controlled by the Koutu Reservoir,analyses the changes in the hydro-meteorological elements in the basin controlled by the Koutu Reservoir and quantifies the influence of climatic factors and human activities on the Koutu Reservoir.It provides data and theoretical support for the deployment and sustainable use of water resources in the Koutu Reservoir under different scenarios,which is of great significance for ensuring local agricultural production and water security.The main research contents and results of this paper are as follows:(1)Analysis of the change pattern of hydro-meteorological elements in the control basin of Koutu Reservoir.This paper adopts linear regression method,Speannan rank correlation test method,M-K mutation test method,sliding t-test method and wavelet analysis method to study the change pattern of inlet runoff of Koutu Reservoir and precipitation and potential evaporation in the basin controlled by Koutu Reservoir from 1980 to 2018,and the results show that:precipitation and inlet runoff depth show no obvious decreasing trend,potential evaporation shows obvious The first main cycle of annual precipitation,annual potential evaporation and annual potential evaporation is 29a time scale.The abrupt changes in annual precipitation were in 1997 and 2002,and the abrupt changes in annual runoff depth were in 1997 and 2004,while no significant abrupt changes in annual potential evapotranspiration occurred during these 39 years.(2)Establishment of the SWAT model of the Koutou Reservoir control basin.Based on the land use type,soil data and meteorological data of the basin controlled by the Koutou Reservoir,a SWAT model of the basin controlled by the Koutou Reservoir was established,and the study area was finally divided into 27 sub-basins with 226 corresponding hydrological units by SWAT modelling.In this paper,28 parameters were selected and the sensitivity of the selected parameters was assessed using SWAT-CUP software.The results show that the saturated soil capacity,the mean slope length,the main channel Manning factor,the baseflow alpha factor,the effective infiltration coefficient of river alluvium and the Manning factor n of slope diffuse flow have high sensitivity to runoff.In this paper,1980-1981 is set as the warm-up period,1982-1989 is set as the rate period,and 1990-1996 is set as the validation period.After the rate setting and validation of the model the final results show that the two indicators,NSE and R2,are 0.91 and 0.85 for the rate period,and 0.89 and 0.88 for the validation period,indicating that the simulation is The NSE and R2 for the validation period are 0.89 and 0.88 respectively,indicating that the simulation is excellent and can be used to simulate the incoming runoff from the Koutou Reservoir.(3)Influence of climate change and human activities on inlet runoff from Koutou Reservoir.According to the sudden change point of inlet runoff,the period from 1980 to 1996 was divided into the base period,the period from 1997 to 2003 was divided into the change periodl and the period from 2004 to 2018 was divided into the change period2,and the influence mechanism of climate factors and human activities on the inlet runoff was analysed.The results of the two methods are consistent and reliable.The results show that the analysis by the elasticity coefficient method and the hydrological simulation method yielded that the contribution of climate change to the reduction of runoff into the reservoir in the change period 1(1997-2003)ranged from 56.67%to 63.33%,and the contribution of human activities to the reduction of runoff into the reservoir ranged from 36.67%to 43.33%;The contribution of climate change to the reduction of runoff into the reservoir in Change Period 2(2004 to 2018)ranged from 14.49%to 25.42%,and the contribution of human activities to the reduction of runoff into the reservoir ranged from 74.58%to 85.11%.C ompared with the base period,the contribution of climate change to the reduction of inlet runoff in change period 1 is higher than that in change period 2,while the contribution of human activities to the reduction of inlet runoff in change period 2 is higher than that in change period 1,indicating that the contribution of climate change to the change of inlet runoff is gradually decreasing,while the contribution of human activities to the change of inlet runoff is gradually increasing as climate changes and human activities intensify.