| Groundwater is a life-sustaining resources.It plays significant roles in health of ecosystems and sustainable development of human societies and economies as well,especially in cold and semiarid regions,where surface water resources are relatively deficient.Comprehensive studies on the recharge sources of regional groundwater form the foundation for the rational utilization of groundwater resources.Such studies will inform steps toward scientific management and sustainable development of regional water resources.In this study,integrated application of hydrochemistry,isotope characterization and hydrological geological data.Observatories for groundwater level,lake water level and water sample sites were set up around the Qinghai Lake.We analyzed the spatio-temporal characteristics of stable isotope and hydrochemistry of precipitation,river water,groundwater and lake water to investigate the recharge source of groundwater around the Qinghai Lake.The main results as follow:(1)The?2H values of precipitation ranged from-192.19?36.32,whereas the?18O values of precipitation ranged from-25.18?4.71.The LMWL was simulated?2H=7.80?18O+10.60.The?2H values of river ranged from-69.36?-28.32,whereas the?18O values of river ranged from-10.91?-3.70.The hydrochemical type of most of the river samples was Ca2+-Mg2+-HCO3-;the hydrochemistry was primarily controlled by carbonate dissolution during runoff.The slope of LEL of river in time showed April(6.71)>October(6.63)>July(5.91)>January(5.83)>August(5.57).The slope of LEL of river in space showed Quanji River(8.01)>Shaliu River(6.86)>Heima River(6.30)>Buha River(6.24)>Daotang River(5.77)>Ganzi River(5.64)>Haergai River(5.28).The?2H values of lake ranged from-26.31?3.82,whereas the?18O values of precipitation ranged from-4.02?1.50.The slope of LEL of lake in space showed Erhai(6.24)>Qinghai Lake(5.75)>Gahai(3.84)>Haiyanwan(2.59).The hydrochemical type of the lake samples was Na+-Cl-.(2)The depth below surface of groundwater ranged from 1 to 16.7 m(mean=4.38m)around the Qinghai Lake.The annual mean value of the depth below surface of groundwater ranged from 0 to 2.3 m(the annual mean=0.8 m).The difference of altitude between the groundwater level and the level of water in the Qinghai Lake was calculated.This difference in altitude ranged from-0.41 to 141.25 m.The values of hydraulic gradient ranged from-0.06to 13.47.Therefore,this indicated that most of the groundwater flowed into the lake.The abundant water periods in Gangcha,Buha River,Hunan,Erhai,Haiyanwan and Gahai were in May,July,September,November,August and March,respectively.The dry water periods were in March,January,February,July,March and October,respectively.The?2H values of groundwater ranged from-65.34?-36.96,whereas the?18O values of precipitation ranged from-10.06?-5.84.Most of the isotope points of groundwater were present close to the LMWL;the LEL of groundwater was simulated as?2H=6.59?18O-3.01,where the slope of LEL(6.59)was lower than that of the LMWL(7.80).This indicated that groundwater in the vicinity of the Qinghai Lake was primarily recharged by local precipitation that had undergone varying degrees of evaporation before infiltration into the ground.The slope of LEL of groundwater in time showed April(7.18)>January(6.89)>July(6.81)>October(6.43)>August(5.74).The slope of LEL of groundwater in space showed Erhai(6.69)>Hunan(6.35)>Buha River(5.71)>Hubei(5.01)>Huxi(4.85)>Shaliu River(3.70)>Haiyanwan(3.09)>Gahai(1.40).The groundwater in the vicinity of the Qinghia Lake was slightly alkaline.The TDS content values of the groundwater ranged from 270.73?4287.87 mg/L(mean values of 692.93 mg/L).The TH content values of the groundwater ranged from 132.29?2550.37 mg/L(mean values of 242.24 mg/L).The hydrochemical type of most of the groundwater samples was Ca2+-Mg2+-HCO3-;the hydrochemistry was primarily controlled by carbonate dissolution during runoff.(3)The recharge types of groundwater in the Qinghai Lake Basin can be summarized as four types:(1)rapid recharge of underground runoff;(2)slow recharge of underground runoff;(3)main recharge of river water and(4)main recharge of underground runoff.There are 38.5%of groundwater quality in the area around the lake exceeding the national standard.Therefore,scientific planning,engineering,and management of livestock manure and wastewater discharge in regions practicing animal husbandry is crucially and urgently requited to not only provide water resources that are safe for drinking but for the sustainable development of the environment of the Qinghai-Tibet Plateau as well. |
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