南水北调西线工程水源区和受水区降水变化及丰枯遭遇特征分析

Trends of precipitation and characteristics of wetness-dryness encountering in the water source and receiving areas of the west route of the South-to-North Water Transfer Project

基于规划中的南水北调西线工程区域内274个国家气象站1961—2022年逐日降水资料,分析了西线工程水源区和受水区年和四季降水量的时空分布特征,以及两区降水的丰枯遭遇特征。结果表明:近62年来,南水北调西线工程水源区年降水量总体呈增多趋势,而受水区年降水量没有明显变化趋势;夏、冬季水源区和受水区降水量均增多,春、秋季水源区降水量增多而受水区降水量减少;年和春、夏、秋季水源区枯水频率均低于受水区枯水频率,并且水源区枯水频率呈减少趋势,而丰水频率呈增加趋势;水源区和受水区年和四季降水丰枯异步频率普遍在60%以上,远大于丰枯同步频率,有利调水的5种丰枯遭遇在年和春、夏、秋季发生频率均超过50%。总体而言,南水北调西线工程水源区和受水区的降水具有较强的丰枯补偿性,且1971年以来有利调水发生频次呈增加趋势,理论上存在保证供水的可能性。但水源区出现连续枯水年的频次较多。因此,在南水北调西线工程规划设计和运行调度时需充分考虑水源区和受水区降水的变化。

Based on the daily precipitation data from 274 national meteorological stations in the west route of the South-to-North Water Transfer Project area from 1961 to 2022,the spatiotemporal distribution characteristics of annual and seasonal precipitation in the water source and receiving areas were analyzed,as well as the characteristics of the encounter between dryness and wetness in the two areas.The results show that in the past 62 years,the precipitation in the water source area of the west route of the South-to-North Water Transfer Project showed an increasing trend,while the trend of precipitation in the water receiving area was not significant.The seasonal precipitation of summer and winter in both water source area and receiving area increased.The precipitation of spring and autumn in water source area increased while that in water receiving area decreased.The frequency of dryness in water source area was lower than that in water receiving area in spring,summer,and autumn.The frequency of dryness in water source area showed a decreasing trend,while the frequency of wetness showed an increasing trend.The asynchronous frequency of annual and seasonal precipitation in the water source area and receiving area was above 60%,which was much higher than the synchronous frequency.The five types of dryness-wetness encountering favorable for water transfer occurred at a frequency of over 50% in spring,summer,and autumn.In general,the precipitation in water source and receiving areas of the west route of the South-toNorth Water Transfer Project had a strong compensatory effect,and the frequency of dryness-wetness encountering favorable for water transfer increased after 1971,ensuring the possibility of water supply.However,the frequency of continuous dryness years in water source area was high.Therefore,it is necessary to consider climate changes of precipitation in water source and receiving areas in the planning,design,and operation scheduling of the west route of the South-to-North Water Transfer Project.