气候变化下党河山区冰雪消融对中下游灌溉的影响研究

In the context of global warming, the mountain cryosphere has indeed undergone considerable changes. Changes of snow cover and glaciers directly affect the runoff from mountain regions. Impacts of cryosphere change on runoff changes from mountainous watersheds and on the downstream irrigation demand have not yet been fully understood at present. This study took the Dang River basin originating from western Qilian Mountains as an example and studied the impacts of glaciers and snow-pack melting on the downstream irrigation demand. The main works include: (1) The Water and Energy Budget-based Distributed Hydrological Model (WEB-DHM) was calibrated and validated from a lot of situ observation data and remote sensing data. The cryosphere process and runoff from mountainous watersheds will be simulated accurately. (2) The daily total runoff and its components, including precipitation runoff, snow-melt runoff, and glacier runoff, during 1980-2099 are simulated based on the validated model. The contributions of each component and the time of tipping point (peak water) of glacier runoff will be revealed from the simulated results. (3) The Environmental Policy Integrated Climate (EPIC) model is employed to simulate the daily irrigation water demand in the mid- and down-stream oasis region. Based on the simulated runoff and irrigation, the balances of water supply and demand in different decades are identified. The results can provide scientific bases and supports for water resource management in Dang River. This study could provide a new method and decision support for water resource assessment and management of an inland river basin in the arid area.

气候变化下高寒山区冰冻圈变化显著，冰雪消融变化直接影响山区径流过程和出山口总径流。目前对出山口径流与山前绿洲灌溉需水量的供需动态平衡关系尚缺乏以模型为手段的过程解析与系统研究。项目以党河流域为对象，开展山区冰雪消融对中下游灌溉的影响研究，主要包括：(1)基于多源观测和卫星产品对党河流域寒区水文模型(WEB-DHM)进行充分验证，实现对源区冰冻圈过程及出山口径流的准确模拟；(2)基于验证后的WEB-DHM模型，模拟历史和未来出山口径流总量及各径流组分(降雨产流、冰雪融水等)，揭示出山口径流变化与降水变化和冰雪消融过程的定量关系，厘清党河源区出山口径流对气候变化的响应规律；(3)基于EPIC模型模拟流域中下游绿洲逐日灌溉需水量，结合模拟的逐日出山口径流量，揭示山区冰雪-山前绿洲流域系统的灌溉水资源供需动态平衡关系。本研究可为干旱区内陆河流域综合水资源管理提供新的方法和决策支持。

气候变化和社会经济发展对干旱半干旱区水资源供需的影响是目前研究的热点问题。对典型区全球变化下水资源及其供需关系，以及人类活动对其影响的研究可为干旱缺水区流域综合水资源管理提供方法指导和决策支持。本项目在构建基于水热平衡观测网络的党河高寒山区数据库和党河中下游绿洲数据库的基础上，解析了近30年敦煌绿洲范围的变化；模拟了党河出山口径流；计算了主要农作物(春小麦、春玉米和棉花)的灌溉需水量；评估了典型水利工程对受水区水资源供需关系的调节作用，及其对工农业生产的影响。研究结果表明，1）近年来，在气候变化和社会经济发展综合影响下，敦煌绿洲面积不断扩大且向东北扩展。相对于1990年来说， 2000、2010和2020年绿洲面积依次增加49.95、172.19和192.58km2。2）WEB-DHM模型基本可以模拟党河山区径流。其中，党河山区年积雪融水径流呈现上升趋势，上升速率为每10年2.1mm；就不同季节而言，春夏秋季均呈现上升趋势，冬季积雪融水经历呈现下降趋势。上升速率最大的是夏季，为8.6mm/10year。3）就敦煌绿洲三种典型农作物春玉米、春小麦和棉花来说，灌溉需水量最大的是棉花，1951-2012年平均灌溉需水量为832mm/年。历史时期(1951-2012年)，三种灌溉需水量均呈现下降趋势。在21世纪，受气候变暖的影响，三种典型农作物的灌溉需水量均呈现增加趋势，并且高排放情景增加速率大于低排放情景。春玉米、春小麦和棉花的灌溉需水量增加速率分别为每十年5.28-23、2.55-23和5.74-30.47mm。4）跨流域调水工程在一定程度上以缓解受水区水资源短缺问题。在全球升温1.5℃的情景下，南水北调工程最大可能给黄淮海流域带来5070 亿RMB/年的效益，同时可使得该区域粮食产量增加115.3 Tcal/年。本研究能够为干旱区水资源管理提供重要的科学依据。