Study On Runoff Processes In Shaliu River Basin Of Qinghai Lake

Runoff processes in Qinghai Lake basin in where a significant belt to maintain the ecological balance in Qinghai-Tibet plateau's northeast are not studied sufficiently.Shaliu River basin located in the north of Qinghai Lake basin is an ideal area for the study of runoff processes.Thus,based on the hydrogen and oxygen stable isotope compositions(?2H and ?18O)of rain water,river water,groundwater,soil water,ice and snow that collected in the Shaliu River basin during 2018-2019,this study clarified the spatial-temporal characteristics of ?2H and ?18O in different water bodies,discovered and quantified recharge relationship and ratio among different supply source,as well as further disclosed runoff processes of river water and groundwater.The results showed that:(1)Hydrogen and oxygen stable isotope compositions on rain water were gradually negative,positive and negative from ablation,rainy to freezing periods because of air temperature,precipitation and water vapor source.Hydrogen and oxygen stable isotope compositions on ice were negative and positive gradually from rainy period,middleaftermost freezing period to ablation period as a result of air temperature.Hydrogen and oxygen stable isotope compositions on river water were fluctuating due to air temperature,precipitation and source of recharge in study period.Hydrogen and oxygen stable isotope compositions on soil water were positive,negative and positive gradually from ablation period to middle-aftermost rainy period on account of air temperature and precipitation.Hydrogen and oxygen stable isotope compositions on groundwater were positive,negative and positive gradually from middle-aftermost freezing period,ablation period to rainy period on the influence of air temperature and precipitation.(2)Hydrogen and oxygen stable isotope compositions on rain water were positive,negative and positive from alpine steppe,alpine meadow to alpine desert belts,respectively,as result of altitude effect and spatial distribution of precipitation.Hydrogen and oxygen stable isotope compositions on ice and river water were gradually negative from alpine desert,alpine steppe to alpine meadow belts,which affected by altitude and spatial distribution of precipitation.Hydrogen and oxygen stable isotope compositions on groundwater were positive at near riverway of alpine steppe belt and negative in other areas because of the spatial distribution of supply source.(3)Surface runoff in the alpine steppe,alpine meadow and alpine desert belts was respectively supplemented by 19.55±0.04% rain water,64.97±0.04% ice,15.49±0.04% snow,73.21±0.50% ice,26.79±0.50% snow,18.05±11.01% rain,25.56±11.01% ice and 56.39±11.01% snow during the ablation period.During the rainy period,the surface runoff in the alpine steppe,alpine meadow and alpine desert belts was replenished by rain water and soil water,and the percentages were 22.11±0.43%,77.89±0.43%,40.11±0.45%,59.89±0.45%,80.02±0.43% and 19.98±0.43%,respectively.In the freezing period,the surface runoff in the alpine steppe,alpine meadow and alpine desert belts was made up by snow and ice,and the proportions were 74.20±0.04%,25.80±0.04%,91.82±0.30%,8.18±0.30%,91.86±0.41% and 8.14±0.41%,respectively.In the study period,the surface runoff in the alpine steppe,alpine meadow and alpine desert belts was supplemented by precipitation(rain and snow)and soil water,and the proportions were 6.84±0.17%,93.16±0.17%,14.89±0.42%,85.11±0.42%,32.87±3.83% and 67.13±3.83%,respectively.(4)Subsurface runoff in the alpine steppe and alpine meadow belts was replenished by rainstorm-ice-snow,and ice-snow,respectively,with proportions of 22.04±0.04% and 70.20±0.04%,7.32±0.04%,98.56±0.28% and 4.44±0.28% during the ablation period.The subsurface runoff in the alpine steppe and alpine meadow belt was replenished by rainwater and soil water,and the percentages were 11.05±0.35%,88.95±0.35%,16.92±0.47% and 83.08±0.47% during the rainy period,respectively.During the freezing period,subsurface runoff in the alpine steppe and alpine meadow belt was fed by ice and snow,and the percentages were 76.66±0.09%,23.34±0.09%,73.11±0.49% and 27.89±0.49%,respectively.In the study period,subsurface runoff in the alpine steppe,alpine meadow and alpine desert belts were replenished by precipitation(rain and snow)and soil water,and the proportions were 7.71±0.16%,92.29±0.16%,8.62±0.41% and 91.38±0.41%,respectively.(5)The supply sources of surface runoff and subsurface runoff in the alpine steppe belt changes from rain water,ice and snow in the ablation period to rain water and soil in the rainy period and then to ice and snow in the frozen period.The recharge sources of surface runoff and subsurface runoff in the alpine meadow belt changed from ice and snow in the ablation period to rain water and soil water in the rainy period and then to ice and snow in the frozen period.The recharge sources of surface runoff in the alpine desert belt changed from rain,ice and snow in the ablation period to rain and soil water in the rainy period and then to ice and snow in the frozen period.The temporal difference of surface runoff and subsurface runoff process was mainly related to air temperature and precipitation.(6)The replenishment effect of surface runoff from the alpine desert,alpine meadow to alpine steppe belts gradually increased during the ablation period,while the replenishment effect of snow gradually decreased,which was mainly related to the spatial distribution of ice and snow.In rainy period,the replenishment effect of surface runoff from the alpine desert,alpine meadow to alpine steppe belts gradually weakened,and the replenishment effect of soil water gradually increased,which was related to topography,soil and vegetation cover.During the freezing period,the replenishment effect of surface runoff from the alpine desert,alpine meadow to alpine steppe belts gradually weakened,and the replenishment effect of snow gradually increased,which was related to the surface freezing mechanism.During the study period,the recharge effect of precipitation(rain and snow)on surface runoff was gradually weakened,but soil water was gradually strengthened from the alpine desert,alpine meadow to alpine steppe belts.In the three periods and the whole study period,subsurface runoff was affected by rainwater,snow,ice and soil water in the alpine meadow and alpine steppe belts without obvious spatial characteristics,which was related to topography,soil and vegetation distribution.