Effects Of Environmental Changes On Runoff Situation In The Tuwei River Basin

The impact of climate change and human activities on runoff can not be neglected,climate changes could affect the flow of runoff,human activities could make huge changes in the underlying surface in a short period of time,leading to the changes in the hydrologic process.Soil erosion is serious in the middle Yellow River and its ecological environment is very fragile.Since the 1960s,a large number of human activities such as soil and water conservation,coal mining,water conservancy projects,groundwater development and so on,varying degrees to change the underlying conditions of the basin,so that the runoff situation and flood in the region over the past few decades has undergone great changes.In the paper,the Tuwei river basin is took as a case study,which was based on the analysis of the annual means ' change scale,the annual distribution scale and the flood scale,and explored the influence of the environmental change on the runoff by using many statistical methods and models.The main research results are as follow:(1)The meteorological elements and the changes of runoff in anmal means were studied.By selecting runoff data series of 1967-2010,precipitation and latent evapotranspiration,and analyzing their change in annual distributions,it was found that although the meteorological elements have resulted a small decrease on runoff,the variation of runoff depth was very strong,and this phenomenon was different from that of meteorological elements,so it is likely to be related to the impact of human activities.The diagnosis of the mutation was 1979 and 1996,and the Budyko equation was used to quantitatively calculate the contribution of climate change and human activities to the changes over the years,and the results showed that runoff depth reduced 32.66mm from 1967-1978 to 1979-1995,climate change contribution was 57.95%,and human activities contribute was 42.05%.The 1996-2010 runoff reduced 55.07mm compared with 1967-1978,the contribution of climate change was 24.19%,and the contribution of human activities was 75.81%.The influence of human activities lead to a decrease in the runoff and the degree was gradually increasing,and the influence of climate became weaker gradually.(2)The changes of meteorological elements and annual distribution of runoff were studied.The runoff depth and precipitation,the potential evapotranspiration were analyzed through the parameters of uneven coefficient,full adjustment coefficient and concentration degree,the results showed that the concentration of precipitation was the highest,the concentration of latent evapotranspiration was lower,the concentration of runoff was the lowest,and their changes are consistent,all of which showed decline-rise-decline.The diagnostic results of the variability of the annual distribution of runoff deep was 1996,then quantified the contribution of climate change and human activity to changes the runoff deep in the annual distribution by the comparison of cumulative slope rates,and the results showed that climate change and human activities contributed 77.67%and 22.33%in terms of variation in the uneven coefficient,the contributions of climate change and human activity were 61.28%and 38.72%respectively in terms of variation in the total adjustment coefficient,the contributions of climate change and human activity were 58.38%and 41.62%in terms of variation in the concentration degree.Climate change was the main influencing factor of the annual distribution of runoff,which determines the concentration degree of runoff,but the influence of human activities on the distribution of runoff was obviously.Climate change caused the concentration of runoff to increase,but the human activity was the homogenization,in general,the impact of climate change was the main factor.(3)In this paper,the changes of the elements of flood were analyzed.The results show that the error of flood peak and flood is less than 20%by TVGM model and the applicability of the model was good.15 rainfall processes were used to simulate flood in three stages,and the changes of flood elements(peak,flood and flood peak)were found to be basically consistent,and studies showed that human activities affected the underlying surface,such as the destruction of vegetation by coal mining,and the restoration of vegetation.In the 1979-1995 stage,the flood peak became higher,flood was bigger,and the flood peak lag was short,and in the 1996-2010 stage,the flood peak became lower,the flood was smaller,and the flood peak lag was longer.