Runoff Variation Characteristics For Datong River And Its Influencing Factors

Since the 20 th century,the impact of human activities and climate change on water resources has become increasingly prominent.The impacts of human activities,such as water diversion across the Datong River basin,have been increasing gradually on the hydrological process of the Datong River.It is important to find out the changes of water resources in the basin,and at the same time to explore and evaluate the influencing factors and extent of climate change and human activities,which is of great significance to the planning,allocation and sustainable utilization of water resources in the basin in the future.This paper aims to analyze the characteristics and rules of hydrometeorological elements and land use types in Datong River Basin from 1956 to 2013,and explores the relationship between runoff and the factors affecting runoff,and calculates the impact rate of the factors.Firstly,the temporal variations of runoff,temperature and precipitation in Datong River Basin are explored.Then,the methods of wavelet and the M-K catastrophe test are used to analyze the variation characters of runoff,precipitation and temperature.Besides,the structure characteristics,change degree and direction of land use types are analyzed using the land use dynamic rate,comprehensive index and transfer matrix,and the relationship between runoff and temperature and precipitation is analyzed based on the multiple linear regression.Finally,we adopt the double mass curve of precipitation-runoff to investigate the influences of the precipitation and other influencing on the Datong River runoff change.The results are shown as follows:(1)The annual runoff variability is uneven at Gadatan,Tiantang,Liancheng and Xiangtang Hydrological Stations in the main stream of Datong River,while the interannual variation is obvious.The runoff trend is basically same at three stations before 1990.The upstream of the main stream of Datong River has less inflow in 1990 s.The runoff in the middle reaches show a significant increase after 2000,but the runoff at the downstream Xiangtang Station decreases obviously.In the future,the runoff in the upper and middle reaches will increase,and decrease in the downstream.The time of annual runoff change time is inconsistent at upstream and downstream catchment with variable cycle years,which the small cycle conversion at downstream catchment is more frequent than at upstream catchment.(2)The interannual variation of temperature is basically consistent in the upper and lower reaches catchment,and the results of abrupt change test show that there is a significant upward trend after 1994;the annual precipitation generally shows a gentle upward trend,and the upstream precipitation increases obviously.The precipitation in the middle reaches has been stable for nearly 50 years,while the downstream shows a downward trend.The abrupt change test shows that the precipitation in the upper and middle reaches changes abruptly in 2002,but there is no obvious abrupt change in downstream runoff.(3)The main land use types in Datong River Basin are grassland and forest,with the area of 70%;the proportion of cultivated land,construction land and water area distribution is very small,with cultivated land accounting for about 7.4% of the basin area.On the whole,the vegetation coverage is good.The comprehensive index of land use in the lower reaches is higher than that in the upper and middle reaches,and the transfer proportion between land use types is very small in 1990-2010.The variation of land use change has little effect on runoff during this period.(4)There is a significant positive correlation between runoff and precipitation in the whole basin.However,a negative correlation exists between runoff and temperature in the upper and lower reaches,and a positive correlation is found between runoff and temperature in the middle reaches.The influence of annual precipitation factor on Runoff is positive in upstream region,but the effect of the other factors is negative.Positive contributions of precipitation and other factors on the runoff is found Precipitation and other factors,though the influence is relatively small.Human activities and other factors have a stronger impact on downstream runoff since 1995,and the impact rates on runoff are-92.54% and-135.36% in1995-2007 and 2008-2013,respectively.