Responses of runoff in Hulun Lake basin of Inner Mongolia to climate change

By using Mann-Kendall non-parametric test,this paper analyzed the climate changes and their effects on the runoff in Hulun Lake basin in recent 50 years,based on the air temperature,precipitation,and evaporation data from 1961 to 2010 and the runoff data from 1961 to 2008.In the study area,the air temperature in 1961-2010 had an obvious increasing trend,the annual precipitation was greatly affected by summer precipitation and experienced four stages,i.e.,increased in 1961-1964 and 1983-2003 and decreased in 1964-1983 and 2003-2010,and the annual evaporation retained a relatively stable state before 1973,had a decreasing trend in 1973-1998 and an increasing trend in 1999-2005,and then decreased,with an abrupt change point in 2005.The evaporation in summer and autumn corresponded well with the precipitation in summer.The runoff was plentiful in 1961-1965 and 1987-2002,but scarce in 1965-1987 and 2002-2008,with a significant decrease in 1975 to 1980.With the increase of air temperature,precipitation presented an overall decreasing trend,which determined the evaporation change to a great degree,and thus,the Hunlun Lake basin appeared a warming and drying tendency.On the basis of the runoff variation characteristics,a comparison was made on the change processes of the runoff,air temperature,precipitation,and evaporation.Correlation analysis indicated that the air temperature,precipitation,and evaporation in summer and autumn were the primary causes of the runoff variation in the Hunlun Lake basin.