Study On Runoff Response Of Min-tuo River Basin Under Complex Changing Environment

The study on the response of watershed runoff to complex changing environment has become one of the hot directions in the development of water science in recent years,as a component and important embodiment of the changing environment,climate change and land use change are gradually strengthening the instability and imbalance of the hydrological cycle,thus affecting the distribution,composition and total amount of water resources,as well as reproducibility and controllability.Furthermore,it brings great challenges to water ecological security,flood control security,water supply security and so on.It is very important to reasonably analyze the response of runoff to climate change and land use change,and it also becomes a difficulty in hydrological cycle research.This paper takes Min-Tuo River Basin as the research area.The Mann-Kendall method and the cumulative anomaly method are used to analyze the interannual variation trend and abrupt trend characteristics of rainfall and temperature in Min-Tuo River Basin in the past 34 years(1981-2014).And arc GIS software was applied to analyze the changing characteristics of the land use in the three periods of 1985,2000 and 2015 in Min-Tuo River Basin,so as to analyze the changes of land use in the basin.Min-Tuo River Basin is divided into four sub-basins: qingyijiang river,dadu river,minjiang river and tuojiang river.And the SWAT model applicable to Min-Tuo River Basin is applied to analyze and study the sensitivity of climate change and land use change to runoff in the four sub-basins.The main conclusions are as follows:(1)Based on Arc GIS,the SWAT model of Min-Tuo River Basin is constructed.Combined with the runoff data of hydrological stations in the basin,the model is calibrated and verified by SWAT-CUP.The results show that the R2 and NSE values of each hydrological station in the calibration and verification period are greater than the model evaluation standard,and the SWAT model can be well applied to Min-Tuo River Basin.(2)From the meteorological data of Min-Tuo River basin,it can be found that 1995 year is a sudden change year of rainfall and temperature.And during 1981-2014 year,the annual average rainfall in the basin shows a general decreasing trend.And the annual average temperature in the basin shows an overall increasing trend.From the land use data of Min-Tuo River basin,it can be found that the basin is dominated by cultivated land,forest land and grassland.From 1985 to 2000,the cultivated land and forest land decreased,while the grassland increased.From 2000 to 2015,the cultivated land decreased,and the woodland and grassland increased.Moreover,the transfer of land use mainly occurs between cultivated land,woodland and grassland.(3)Based on the analysis of the changes of the average annual runoff under different climate scenarios,it is known that there is a positive correlation between runoff and rainfall and a negative correlation between runoff and air temperature in Min-Tuo River Basin.Under the climate change scenario,the runoff change of dadu river is the largest and that of qingyijiang river is the smallest in Min-Tuo River Basin.(4)By analyzing the runoff changes under a single land use change scenario,it can be seen that the transformation of all cultivated land into forest land or grassland in Min-Tuo River Basin will reduce the runoff,and the runoff in minjiang river and tuojiang river will decrease greatly.The conversion of all forestland into grassland in the basin will lead to the increase of runoff in Min-Tuo River Basin and a greater increase in the runoff of dadu river and minjiang river in the basin.(5)By studying the runoff changes of the watershed under different tillage patterns and rotation and fallow scenarios,it is known that contour tillage,strip tillage,crop residue tillage,no-till and crop rotation will lead to the reduction of runoff in Min-Tuo River Basin,among which,the runoff of minjiang river and tuojiang river decreases greatly;under the scenario of returning farmland to forest and grass cultivation,the runoff of Min-Tuo River Basin will also decrease,and the runoff of minjiang river and dadu river in the basin will decrease greatly.(6)Both climate change and land use change will lead to different degrees of changes in runoff in Min-Tuo River Basin,among which the impact of climate change on runoff is significantly greater than that of land use change.In terms of runoff change in four sub-basins,dadu river runoff is most affected by climate change,while minjiang river runoff is most affected by land use change.Therefore,in the future water resources management of Min-Tuo River Basin,more attention should be paid to the trend of climate change and corresponding management measures should be taken to promote the healthy and sustainable development of the water ecological environment in Min-Tuo River Basin.(7)Through the analysis of the internal water resources of Min-Tuo River Basin,we can see that dadu river and qingyi river are rich in water resources,while minjiang river and tuojiang river are scarce.The problem of water resources in minjiang river and tuojiang river can be solved by implementing inter-basin water transfer scheme.In years with abundant water resources,water was transferred from dadu river to minjiang river and tuojiaang river,and from qingyi river to minjiang river and tuojiang river in years with scarce water resources.