湖南紫鹊界梯田自流灌溉系统降水条件

Rainfall Condition of Artesian Irrigation System of Ziquejie Terrace in Hunan Province

为了全面认识湖南紫鹊界梯田系统的水循环机制,从降水条件的视角出发,基于紫鹊界地区及周边共11个气象站的1986—2015年降水序列数据,运用集中度、标准化降水指数等方法从降水量、降水年内分配、干旱频率等方面开展对比分析,以揭示紫鹊界地区梯田稻作自流灌溉系统所拥有的独特的天然降水条件.结果表明:紫鹊界地区3个气象站多年平均降水量达1638.7 mm,比外围8个站平均高出177.4mm,其中夏季(6—8月)平均降水量为675.1mm,比外围8个站平均高出122.4mm;紫鹊界3个站旬降水序列的平均集中度为0.373,明显高于外围8个站的平均值0.354,夏季是紫鹊界地区降雨的主要优势时段,多年平均降雨高峰为6月中旬,晚于外围8个站的6月上旬或5月下旬;紫鹊界地区5—8月的3个月时间尺度干旱频率有“先小后大”的特征,其中5月和6月的3个月时间尺度干旱频率明显要小于全区平均值,7月和8月要大于平均值;6月上旬—8月中旬是紫鹊界梯田灌溉的主要时期,紫鹊界地区降水年内分配、多年平均干旱频率分布特征等与紫鹊界梯田的水稻生长期形成良好的匹配关系,降水是紫鹊界梯田自流灌溉系统的重要自然支撑条件.

In order to deeply understand the water cycle mechanism of Ziquejie Terrace in Hunan Province,a comparative study between the Ziquejie region and the surrounding areas was carried out to reveal the superior precipitation condition behind the terraces with the help of the concentration degree(D_(C))and rainfall standard index(I_(SP))methods,based on the precipitation data of 11 meteorological stations in the Ziquejie region and the surrounding areas from 1986 to 2015.The results show that the annual average rainfall in the Ziquejie region is 1638.7 mm,which is 177.4 mm higher than that of the eight outer stations.The average rainfall in summer(from June to August)is 675.1 mm,which is 122.4 mm higher than the eight outer stations.The average D_(C) of ten-day rainfall sequence of the three stations in Ziquejie is 0.373,which is significantly higher than the average value of 0.354 of the eight outside stations.Summer is the main predominant period of rainfall for the Ziquejie Terrace region.The average rainfall peak period in the Ziquejie Terrace region is in mid-June,later than the eight outside stations in early June or late May.The drought frequency of the three-month time scale shows the characteristics of“small first and then large”from May to August in the Ziquejie region:The values of drought frequency in May and June are markedly less than the average value of the whole region,while the values in July and August are just the opposite.The main irrigation period of rice in the Ziquejie region lasts from mid-June to mid-August.The seasonal distributions of rainfall and drought frequency form a good match with the rice growth-period in the Ziquejie Terrace region,which is one of the important supporting conditions of the artesian irrigation system.