Study On The Impact Of Climate Change And Human Activities On Watershed Runoff

With rapid economic growth,the impact of continuous climate change and human activities on the hydrological cycle process is becoming increasingly intense,resulting in a certain change in the temporal and spatial distribution of hydrometeorological elements.Therefore,actively carrying out research on the impact of climate change and human activities on runoff is helpful for understanding the hydrological cycle law in a changing environment,which has certain scientific value and practical significance for watershed water resources management,water resource development,and optimal allocation.This thesis considered the Minghe River Basin as the study area,and based on the analysis of the variation characteristics of hydrometeorological elements,the Soil and Water Assessment Tool(SWAT)distributed hydrological model based on“time-varying parameters”was established,and the effects of climate change and human activities on runoff are quantitatively separated by combining the double accumulation curve method,cumulative slope change rate analysis method,elastic coefficient method,and hydrological simulation method.Based on this,the climate and land-use scenarios were set to further study the response of runoff to climate change and land-use change.The time series and CA-Markov models are used to predict the climate and land-use,the SWAT hydrological model is driven to predict the natural runoff process of Linmingguan hydrological station in 2030,and then adjustments are made to the reservoir according to the different natural inflow of the reservoirs and water intake in 2030 to obtain the actual runoff process considering human activities.The main research results are as follows:(1)The trend,periodicity,and the mutation of hydrometeorological elements were discussed via linear regression,the Mann–Kendall trend,Morlet wavelet method,ordered clustering,and nonparametric Pettitt method.(2)The SWAT model of the Minghe River Basin based on“time-varying parameters”was established.SWAT-CUP was adopt to calibrate and further verify the model in different periods,and the applicability of the model was tested.The results showed that the measured monthly runoff process and the simulated monthly runoff process at each period of the Linmingguan hydrological station fit well,meeting the relevant evaluation criteria,such as correlation coefficient,Nash coefficient,and relative error,which can be used to quantitatively separate and evaluate the impacts of climate change and human activities on runoff.(3)The effects of climate change and human activities on watershed runoff were quantitatively separated using the double accumulation curve method,cumulative slope change rate analysis method,elastic coefficient method,and hydrological simulation method.The results showed that the principles and the required data of the four methods were different,from the attribution results,the impact of human activities on runoff in each period is the main factor,followed by climate change.Based on SWAT model,the effects of reservoir regulation and storage,water intake,land use and other human activities on runoff are quantitatively separated.The results show that water intake is the primary factor of human activities,whereas reservoir regulation and storage take second place.Land use play a negative role in the reduction of runoff;at the same time,the change in runoff is still affected by soil and water conservation as well as other water conservancy projects.(4)By setting different climate scenarios,the response of runoff to climate change was analyzed.The results showed that the runoff was negatively correlated with temperature,and positively correlated with precipitation.The sensitivity of runoff to precipitation changes was greater than that of runoff to temperature change.The response of runoff to land-use change was analyzed by setting different land-use scenarios.The results showed that the order of runoff yield in each land-use scenario was urban land>cultivated land>forest land>grassland.(5)The climate and land-use types in 2030 were predicted using the time series method and CA-Markov model.The SWAT model is used to simulate the natural runoff process of the main control section of Minghe River Basin in 2030,and the actual runoff process of Linmingguan station in 2030 considering human activities is further researched.The results showed that the natural runoff of Linmingguan station in 2030 was affected by the warmer temperature and the increase of construction land,which was higher than that in2011 under the same precipitation condition.According to the natural inflow process in2030,the regulation calculation of the reservoir shows that the actual runoff in 2030 is 7.70million m~3,which changes only slightly compared with the measured runoff in the typical year.Therefore,it is necessary to restore the river ecological environment,tap the water-saving potential of agriculture,industry and life,and strengthen the optimal allocation of water sources and water supply facilities..