洞庭湖水文对流域干旱情势的响应及归因分析

Response of hydrology of Dongting Lake to drought conditions of Dongting Lake basin and its attribution

【目的】极端气候变化加剧了通江湖泊水文情势的波动性,亟需从流域视角探究流域干旱情势对通江湖泊水文环境的影响。【方法】以我国典型通江湖泊洞庭湖及洞庭湖流域为研究对象,选取2010—2020年及2022年极端干旱情景下洞庭湖流域5个代表性气象水文站的降水量、温度、水位等数据,结合水文趋势分析、标准化降水指数(SPI)和回归分析等方法,对洞庭湖流域和湖泊的气象水文演变特征、干旱情势以及湖泊水位与流域干旱情势的响应关系进行了全面分析。【结果】结果表明,研究期间洞庭湖流域降水量呈小幅上升趋势,流域温度变化趋势不显著,但澧水流域温度总体较低,变化范围16.07~17.41℃。洞庭湖水位总体呈波动上升趋势,变化在23.63~25.81 m。洞庭湖流域SPI指数变化在-0.86~0.31,正常和轻旱年份占比分别为91%和9%。流域年内干旱情势总体呈先升后降变化趋势,正常和湿润等级频率分别变化在0.18%~0.64%和0.18%~0.36%。洞庭湖水位与流域降水和径流量呈显著正相关,与温度呈显著负相关。2022年洞庭湖水位呈先升后降变化趋势,6月达到年内水位最高值(30.45 m)后骤降。2022年1—6月洞庭湖流域干旱情势总体处于湿润和正常等级,后降至中旱和重旱等级。【结论】洞庭湖流域年际干旱情况多为正常年份,其余为轻旱年份。与多年月均水位相比,2022年极端干旱情景下洞庭湖水位峰值由往年7月提前至6月,随后水位骤降。此外,4月、5月、7月洞庭湖水位与流域SPI指数显著相关,反映了当前月份湖泊水位对流域干旱情势的深度响应,刻画了流域降水异常引起的洞庭湖“夏旱”特征。以上结果可为水文及农业部门应对气象灾害、实施农业生产保护措施等提供科学参考。

[Objective]The fluctuation of the hydrological regime in river-connected lakes has been exacerbated by the extreme climate change and intensive human activities.Therefore,it is crucial to investigate the impact of drought occurred in basin on the hydrological conditions of river-connected lakes.[Methods]Dongting Lake,a typical river-connected lake in China,together with its basin,were taken as the study object.Five representative meteorological and hydrological stations in Dongting Lake basin were selected from 2010 to 2020 and 2022(a typical drought scenario),including precipitation,temperature,and water level.This study combines the hydrological trend analysis,standardized precipitation Index(SPI),and regression analysis to investigate the characteristics of meteorological and hydrological factors,drought conditions,and the relationship between water level of Dongting Lake and the drought conditions in Dongting Lake basin.[Results]The result showed that the precipitation of Dongting Lake basin displayed a slight increasing trend during the study period.No significant variation in temperature is detected,whereas the temperature of Li river basin exhibited low,ranging from 16.07 to 17.41℃.The water level of Dongting Lake displayed a general fluctuating and increasing trend,ranging from 23.63 to 25.81 m.The SPI of Dongting Lake basin varied from-0.86 to 0.31 during study periods,with the proportion of 91%for normal years and 9%for light drought years.The drought conditions of Dongting Lake basin exhibited a trend of increasing firstly and then decrease,with the high frequency for normal level(0.18%~0.64%)and wet level(0.18%~0.36%).In 2022,the water level of Dongting Lake increased to 30.45 m in June,then decreased sharply.From January to June 2022,the drought condition in Dongting Lake basin is wet and normal levels,but later it deteriorates to moderate and severe drought levels.The water level of Dongting Lake showed a strong positive correlation with the precipitation and water discharge.[Conclusion]The majority of study years in Dongting Lake basin were classified as normal years,while the remaining years were categorized as slight drought years.The peak water level of Dongting Lake in 2022 occurred in June,which is earlier than previous years in July.Moreover,the water level of Dongting Lake in April,May,and July showed a significant correlation with the SPI index of Dongting Lake basin,reflected the response of lake water level on drought condition in the basin,and revealed the feature of“summer drought”in Dongting Lake caused by abnormal precipitation in Dongting Lake basin.Our findings can offer a scientific support for hydrological and agricultural departments in managing meteorological disasters and implementing measures to protect agricultural production.