Research On Runoff Variation And Its Influencing Factors In The Upper Reach Of Ziya River Basin

The upper reaches of the Ziya River are located at the eastern foot of the Taihang Mountains and the North China Plain.It is an important grain production area in China.Since the 1980 s,being effected by multiple factors including increased temperature in the area,accelerated hydrological cycle and intensified human activities,the hydrology circulating law in the Ziya River Basin has become more complicated.In this paper,statistical methods,hydro-thermal coupling balance formula and hydrological model method are utilized to explore the characteristics of runoff changes in the upstream of the Ziya River and their influencing factors.According to the runoff and meteorological data of the upper reaches from 1961 to 2013,an analysis of the trend and abrupt characteristics of runoff changes in the basin,has been conducted combined with the actual conditions of the basin climate,land use types,and human activities,which helps qualitatively analyze the relationship between changes in various factors and changes of runoff.Tthe double cumulative curve method,the Choudhury-Yang hydrothermal coupling model and the SWAT hydrological model,are used to quantitatively calculate the contribution rate of different factors to the change of runoff in the upstream of the Ziya River.Based on the analysis of results,a physical explanation is made for the internal relationship between the changes in above factors in runoff,combined with the hydrological cycle process,.The main conclusions are as follows:(1)Influenced by climate change,human activities and other factors,the runoff in the upper reaches of the Ziya River showed a significant downward trend,with an abrupt change in 1983.According to the test results of the runoff mutation point,the period from 1961 to 1983 is divided into the base period and the period from 1984 to 2013 is the mutation period.(2)Reduced precipitation has a positive effect on runoff reduction,increased temperature has a negative effect,and changes in underlying surface conditions have a positive effect on runoff reduction.The interaction between precipitation,temperature and land use type has a negative effect on runoff reduction,while changes in other factors have a negative effect,among which changes in underlying surface conditions play a leading role in eduction.(3)The calculation results of the double cumulative curve,the hydro-thermal coupling model and the SWAT model show that the contribution rate of precipitation to runoff changes is17.4%～28.3%;the calculation results of the water-heat coupling model and the SWAT model show potential evapotranspiration’s(air temperature)contribution to runoff change is-9.4%～-9.6%,and the contribution rate of underlying surface conditions is 66.1%～88.4%;SWAT model calculation results also give three factors,precipitation,temperature and land use type,at the same time,have the-41.7% contribution rate of changes in runoff changes.Tthe contribution rate of changes in other factors other than these above to runoff changes is-43.1%.Besides precipitation,temperature and land use,significant increased amount of water consumption for residential use and irrigation use caused by the construction of large irrigation areas are the main reasons for the decrease in runoff changes.