Stable Isotopes In Different Types Of Water And Their Significance During The Wet Season In The Urumqi River Basin,Eastern Tianshan Mountains,China

Hydrologic cycle is a bond and core that link the layers of the land surface,environmental isotope as an important part of natural water body, although theproportion is very small, responds to the environment changes sensitively, and recordsthe history of the Hydrological cycle evolution. Hydrogen and oxygen stable isotopesas tracer elements of the hydrologic cycle, not only have differences in different waterbodies, but also depend on latitude, altitude, distance from the shore, season,temperature, precipitation and other factors, so variations of isotopic abundance thatare measured can guide us to know geochemical and hydrologic cycle clearly. Basedon the observation for a full year from September2011to September2012in UrumqiRiver basin, Chinese Tianshan Mountains, samples of ice and snow of Urumqi glacierNo.1, surface water and groundwater of hydrological stations, and precipitation ofmeteorological stations collected, especially the wet season （from May to September,2012）, the study systematically analyzed the composition and distributioncharacteristics of δD and δ¹⁸O, vapor source tracer, environmental and climaticsignificance, as well as hydraulic connection, which helped to clarify the hydrologiccycle process in the inland basin deeply. The results were showed as follows.（1） In the wet season, the δD and δ¹⁸O in precipitation of Urumqi River basin,was higher, changed in a larger range, and presented unimodal curve. The δD andδ¹⁸O in precipitation had a significantly positive correlation with temperature andaltitude, which reflected the unique and nature geographical climate characteristics ofthe arid inland areas. The slope and intercept of Urumqi River basin local meteoricwater line deviated from the global meteoric water line, the slope about7being a signof the unique climate in arid areas, the water line differences between the upper andmiddle reaches and downstream showed that there were different isotopes process andinfluence factors in the upper and middle reaches and downstream. The δD and δ¹⁸Oin precipitation as powerful tracer tools, tracking results showed that the UrumqiRiver basin was affected by the large-scale climatic conditions, as well as localclimate.（2） The δD and δ¹⁸O in surface snow in the wet season at the Urumqi GlacierNo.1had a significant characteristic, the δD and δ¹⁸O in surface snow of east branch had the negative elevation effects, and variations of δD and δ¹⁸O in surface snow ofwest branch fluctuated strongly with altitude change, yet exsiting the elevation effect.The upper and middle section of δ¹⁸O in snow pits, especially the surface snow had alarge range, the bottom section of that having little change, but the overallcharacteristics remain unchanged. The δD and δ¹⁸O in surface snow and snow pit hada good corresponding to the local temperature, reflecting the temperature changesperfectly, especially comprehensive meteorological conditions in the snowaccumulation period. In the wet season, ice and snow melt water by melt andevaporation were relatively obvious, the ablation of east branch started first, being notsynchronical with the west branch, but the δD and δ¹⁸O in ice and snow melt waterchanged synchronically at the end of the melting period. The δ¹⁸O in the ice and snowmelt water decreased slightly under the increase of altitude, showing an elevationeffect, and reflected the synthetical ablation conditions in different altitude above thesample point.（3） The values of δD and δ¹⁸O in the Urumqi River basin from upstream todownstream became higher gradually, and the variation trend was almost the same asthat of Urumqi River basin precipitation. Variations of δD and δ¹⁸O in groundwaterwere relatively small at Houxia hydrological station, but a significant characteristics,enrichment from may to August gradually, the largest at August, decreasing afterSeptember. There was a close hydraulic connection between atmosphere precipitation,surface water, groundwater and ice and snow melt water in the Urumqi River basin, inother words, atmospheric precipitation recharged groundwater, mixing with ice andsnow melt water to supply the surface water, further to supply the groundwater in thewet season. The water lines containing local meteoric water line, surface water line,groundwater line and the isotopic composition in ice and snow melt water in theUrumqi River basin were far away from that of the global meteoric water line, stableisotope has experienced a certain degree of evaporation, and isotope enriched in thewater during the wet season in the Urumqi River basin.