Research Progress on Variations and Effectors of the Runoff in the Source Region of the Yellow River

In recent years,the runoff in the source region of the Yellow River has declined sharply,which threats the water resources and economy in the lower reaches.The present study summarizes the recent research progress on variations of the runoff in the source region of the Yellow River and its response to climate change and human activities.The results show that: the average monthly runoff’s characteristic is unimodal or bimodal,and changes with the year;There are obvious interannual and decadal variation of runoff : the longest period between rich year and dry year is 4 ~ 5 years,and also the time of lasting dry year is longer than rich year.The precipitation is the main positive factor influencing the runoff of the source region of the Yellow River.On other hand,when the temperature rise,the evaporation increase,leading to the reduction of the runoff.In the matter of human activities,the reduced coverage of vegatation and intensified desertification changes the surface conditions and further damages the ecosystem,playing an important role on cutting down the runoff in the source region of the Yellow River.At last,this review concludes that in further studys more attention shoule be paied on the variation characteristics of unimodal and bimodal form of runoffand the influence of the Plateau local thermodynamic properties and atmospheric circulation(such as surface sensible heat and plateau monsoon).Further more,it is worthy to strengthen the quantitative analysis of the contribution of natural factor and anthropogenic factor to the runoff.