石羊河流域冰冻圈融水对出山径流的贡献及影响

摘要

Cryosphere meltwater has been recognized as an important source of local water resources.However,there are a few assessments on the contribution from permafrost active layers groundwater.In this study,taking Shiyang River basin as an example,we quantifies the fraction from permafrost active layers groundwater and glacier snow meltwater to runoff in the basin,an in-land river basin of Northwestern China,where glaciers were disappearing and permafrost was in degradation.A total of 343 event-based precipitations samples at six stations of Xidahe,Jiutiaoling,Anyuan,Wuwei,Yongchang and Minqin in Shiyang River basin,129 river water samples from Dajing River,Gulang River,Huangyang River,Jinta River,Xiying River,Dongda River and Xida River,10 spring samples at mountainous region,11 reservoir water samples,36 permafrost active layers groundwater samples and 22 glacier snow meltwater samples have been collected and analyzed for their isotopic compositions.Results indicated that the runoff is a mixture of precipitation,permafrost active layers groundwater and glaciers snow meltwater in the basin,and there is a frequent exchange between river water and spring water in mountainous region.The shallow groundwater recharging height is at the altitude of 3700m,whereas the deep groundwater is principally maintained by palaeowater with some modern recharge in the basin.Glacier snow meltwater only accounted for 3％ of outlet river water in Shiyang River basin,and this contribution is 7％,5％ and 1％ for three tributaries:Dongda,Xiying and Jinta rivers,respectively.However,with respect to the permafrost active layers groundwater,this contribution rate is 23％ for Shiyang River basin,and is 28％,22％,13％,16％,9％,24％ and 27％ for Dongda River,Xiying River,Jinta River,Xida River,Huangyang River,Gulang River and Dajing River,respectively.As the main runoff area,the contribution from water in glacier and permafrost belt has accounted for 82％ of the outlet river water.The results confirmed that permafrost active layers groundwater has played an important role in runoff of in-land river basins,and it is of great significance to evaluate its influence on hydrological process under climate warming scenario.%气候变暖背景下,随着冰冻圈的持续萎缩,冰冻圈融水已成为寒区径流的重要组成部分和寒区水文过程的关键影响因子.以石羊河流域为研究区,2013年7月～ 2014年6月在系统采集大气降水、河水、泉水、井水、水库水、渠系水、冻土活动层地下水和冰雪融水样品基础上,应用稳定同位素示踪技术,定量评估了石羊河流域冰雪融水和冻土活动层地下水对出山径流的贡献量,结果表明:流域内大气降水、冻土活动层地下水和冰雪融水充分混合后以地下水的形式补给径流,大气降水、冻土活动层地下水和冰雪融水对出山径流的补给率分别为77％、20％和3％.依据多年冻土下界将山区分为冰雪冻土带和植被带,分析证实冰雪冻土带输出水量贡献了出山径流的82％,而植被带贡献了18％.流域出山口径流的补给带为海拔3300m以上,中游浅层地下水的补给带为海拔3700m以上.冰雪融水和冻土活动层地下水对7条支流出山径流的贡献率因自然地理状况而明显差异,东大河、西营河和金塔河降水对出山径流的贡献率分别为72％、78％和87％,相应的冻土活动层地下水贡献率为21％、17％和12％,冰雪融水为7％、5％和1％.降水对西大河、黄羊河、古浪河和大靖河出山径流贡献率分别为84％、91％、76％和73％,冻土活动层地下水对出山径流的贡献率依次为16％、9％、24％和27％.研究确认冻土活动层地下水已成为内陆河流域径流的重要组成部分,未来亟须进一步加强冻土活动层地下水水文机制的研究.