2022年长江流域汛期枯水情势分析

Analysis on low water regime during flood season in Yangtze River Basin in 2022

2022年长江流域出现“汛期反枯”且偏枯严重的异常现象。为定量探讨2022年长江流域汛期枯水情势,基于长江干流及洞庭湖、鄱阳湖水系主要控制站1952~2022年汛期月平均流量序列(考虑了梯级水库调蓄影响),采用P-Ⅲ曲线和适线法分析了干支流主要控制站点的枯水重现期,并基于B值诺模图法探讨了枯水重现期的不确定性,采用典型年法分析了长江流域2022年8月和9月的枯水地区组成。结果表明:①在水量方面,洞庭湖、鄱阳湖两湖水系2022年8~10月来水均为71 a来同期最小或次小,部分月份枯水重现期超70 a一遇。长江中、下游干流8月出现超70 a一遇枯水,来水量均为历史同期实测最小。7~10月长江上游和螺山站枯水重现期约30~60 a一遇,汉口、大通站来水量为实测同期最小。从重现期分析结果来看,2022年长江流域发生了极端干旱。②在来水组成方面,2022年8月和9月长江流域表现为上下同枯、干支同枯,在此期间,螺山、汉口等站来水量占大通站的比例与多年平均占比接近或偏高,而两湖来水占大通站的比例均显著偏小。从枯水地区组成来看,2022年长江流域枯水情势为流域性枯水。③2022年长江中下游梅雨偏早、梅雨量偏少,是导致长江中下游流域性干旱的主要原因之一,流域内梯级水库群蓄水形势严峻;如果预报梅雨期偏早且梅雨量较小,则容易发生夏秋连旱的情况。研究成果可为长江流域干旱分析研究、加强水资源统一调度管理、有效提升旱情应对能力等方面提供技术支撑。

In 2022,the Yangtze River Basin experienced a severe drought during the flood season.In order to quantitatively explore the low water regime during flood season in Yangtze River Basin in 2022,based on monthly average flow series of some control stations on Yangtze River main stream,Dongting Lake and Poyang Lake from 1952 to 2022(taking into account the regulation effect of cascade reservoirs),this paper used P-Ⅲdistribution and curve fitting method to analyze the drought return periods of the main control stations,and discussed the uncertainty of drought return periods based on the B-value nomograph method.The inflow regional composition of Yangtze River Basin in August and September 2022 was analyzed by typical year method.The results showed that:①In terms of water amount,the water volume from August to October 2022 in Dongting Lake and Poyang Lake was the smallest or the second smallest one during the same period in 71 years,and some return periods exceed 70 years.In August 2022,the inflow in midstream and downstream of Yangtze River was the smallest in the history of same period with return period greater than 70 years.The return period in July to October 2022 was about 30~60 years in the upper reaches of the Yangtze River and Luoshan Station,and the inflow of Hankou and Datong Station was the smallest in the same period.The results of return period analysis indicated that an extreme drought occurred in the Yangtze River Basin in 2022.②In terms of the inflow regional composition,the upstream,midstream and downstream of Yangtze River,mainstream and tributaries of Yangtze River all exhibited a severe drought.The proportion of inflow of Luoshan and Hankou Station in that of Datong Station in August and September 2022 was close to or higher than the multi-year average proportion;while the proportion of inflow of Dongting Lake and Poyang Lake in that of Datong Station was significantly smaller in both August and September.From the perspective of inflow regional composition,the drought in the Yangtze River Basin in 2022 was basin-drought.③In 2022,the early and low plum rains in the middle and lower reaches of the Yangtze River were one of the main causes of the basin-drought.The impoundment situation of cascade reservoirs in the basin was serious.If the plum rains are forecasted to be early and small,the consecutive summer and autumn droughts are likely to occur.The research results can provide technical support for drought analysis and research in the Yangtze River Basin,strengthening the unified water resources scheduling and management,and effectively improving the ability to cope with drought.