Study On Stable Isotope Characteristics And Sources Of Precipitation And River Water Of Shiyang River Basin

Water is an indispensable resource for the survival and development of human civilization,especially in arid inland river areas.Under the background of global warming,with population growth and rapid economic development,the lack of water resources is gradually expanding.The northwestern arid region is facing unprecedented water pressure,especially in Shiyang river basin.The study of precipitation and environmental isotopes in Shiyang river basin can provide an important scientific basis for the formation,circulation and transformation process and mechanism of water resources in inland river basin,and has important practical significance in water resources management and water environment monitoring in arid regions.Based on 640 samples of atmospheric precipitation,river water,ground water in permafrost active layer,ice and snow melt water in Shiyang river basin,combined with relevant meteorological data and reanalysis data,the stable isotope characteristics,temporal and spatial variation,and environmental significance of precipitation and river water were studied,and the moisture source of basin atmospheric precipitation and the composition of runoff replenishment were analyzed.The main conclusions are as follows:1)The ?¹⁸O value of precipitation in Shiyang river basin shows the seasonal variation characteristics of high in summer and low in winter,and the stable isotope of precipitation in the basin shows significant"elevation effect"with a variation range of-0.22‰/100m,which is also a reflection of"temperature effect".Temperature plays a leading role in the variation of?¹⁸O value in precipitation,and the"precipitation effect"of stable isotopes in precipitation is not reflected.2)Local atmospheric waterline equation of Shiyang river basin is:?D=7.73?¹⁸O+11.31,R²=0.97.The slope and intercept of the atmospheric waterline are obviously lower than that of the global atmospheric waterline,which reflects the characteristics of it in the arid region,that is,the stable isotopes in precipitation are enriched due to the strong evaporation.The slope and intercept of the atmospheric waterline in study region are higher in winter half year than in summer half year,and higher in mountainous area of high elevation than in oasis area and desert area of low elevation.3)Due to the differences of elevation,vegetational covering,temperature and precipitation,the precipitation isotope changes in desert area,oasis area and mountain area of Shiyang river basin show certain differences:that the stable isotope value of precipitation more affected by evaporation is more positive at desert area and oasis area of low elevation,but that affected by more local recycling water vapor is more negative at mountain area of high elevation,that it can be seen in the local atmospheric waterline,the reverse variation of?¹⁸O and d-excess,and the difference of temperature effect.4)The main source of atmospheric water vapor in the basin is the westerly water vapor transport.In winter half year,it is almost completely transported by the westerly,and the total amount of water vapor is less.In summer,the total amount is larger,which is replenished by the monsoon water vapor under the weather scale besides of the water vapor transportation of westerly.5)On the time scale,the stable isotope value of river water is relatively stable,and its variation range is small,but it shows a certain seasonal variation,that the value of?¹⁸O is slightly higher in summer and slightly lower in winter.On the vertical direction,it shows an altitude effect,and the value of?¹⁸O is slightly negative with the increase of altitude.From northwest to southeast,the values of?¹⁸O and d-excess in different tributaries of river water do not show regular changes,and the difference is small,indicating that there is no regional difference in runoff supply sources of each tributary.6)The main supply source of runoff in Shiyang river basin in June and July is precipitation,followed by groundwater in permafrost active layer,and ice and snow melt water.The supply source of each tributary is basically similar to that of the whole basin,but the supply rate of ice and snow melt water of Xiying river can reach 19%.