Research On The Permafrost Change And Hydrological Response Under The Climate Change In The Upper Reaches Of Heihe River

The distribute and change of permafrost with special confining function are important for the Eco-hydrologic cycle of the upper reaches in Heihe River.Recent years,the permafrost occurs the phenomenon of degradation under the background of the temperature raising up obviously.Because of above,studying the distribution and change of permafrost and the hydrological response has important scientific significance under climate changes.Based on analyzing the climate change features of the upper reaches in Heihe River,taking advantages of Land Surface Temperature by interpolating meteorological stationsdata and MODIS Land Surface Temperature data,usingSpatial analysis function of ArcGIS,the frost number model is applied to simulate the permafrost distribution and analyze characteristics of its spatial-temporalvariation in the upper reaches of Heihe River.Also,freezing-thawing depths of active layer is calculatedwith using shallow surface water or thermal parameters and Stephen formula,and the impacts of geographical factors such as elevation,slope are analyzed on the freezing-thawing depths.Based on nearly 30 years of daily surface runoff data,adopting improved methods Kalinin,the variation of recession index and base flow are calculated and analyzed to probe the relationship between permafrost degradation and recession index,as well as to analyzethat how permafrost degradationimpacts on the runoff,base flow,and the minimum average monthly flow in lacking groundwater observation area.At last,by using deuterium and oxygen isotope technology,end-member mixing model is applied to estimate the components of runoff in the Hulugou catchment,and to probe contribution of different water bodies such as permafrost meltwater make on runoff.The results showed that,during 1980 to 2012 years,the distribution area of permafrost presented a declining trend,and the rate of avenue degradation is about 1.1%/a,and the lifting rate of mean low limit of permafrost is about 12 m/a.Take 2011 as an example,high altitude hillside and the top of the west of the research area had bigger freezing depth,but the lower altitude valleys and the outlets areas of the mountain in northern had smaller frozen depth.So,the freezing depth increases when the elevation increases,and the thawing depth declines.The slope aspect also has big impacts on the freezing and thawing depth.The study found that,the mean low limit of permafrost and distribution areas in west of the research area existed significant positive and negative correlation with the avenue change of recession index.That is to say,when distribution area increases,the mean low limit of permafrost declines,and recession index decreases.By using the change of recession index,the thickening rate of active layer thickness in west of the research area was estimated as 1.3%/a.The permafrost degradation may be one of the reasons which cause the increase of runoff and minimum average monthly flow.These studies have a certain reference value forresearching the hydrological cycle in permafrost regions under climate change.