三峡建库前后洞庭湖水文情势变化分析

Changes in Hydrological Regime of Dongting Lake before and after the Operation of the Three Gorges Reservoir

摘要: 洞庭湖是长江中下游的重要大型通江湖泊，其防洪、生态地位突出。本文采用滑动平均、M-K趋势检验等数理统计方法，分析三峡建库前后的洞庭湖水文情势变化，结果表明：从入出湖径流量变化分析，洞庭湖入湖组成中荆江三口径流量显著下降，三峡建库后减少44%，洞庭四水来水无明显变化，水量占比上四水比例增加、荆江三口比例下降，出湖径流量呈显著下降趋势，三峡建库后减少了12.8%，主要来自于荆江三口径流量的减少；从湖区代表站七里山站特征水位变化分析，年际、年代际均呈显著上升趋势，三峡建库后七里山站平均水位抬高0.18 m，逐月平均水位具有汛前水位抬高、汛后水位降低的特点，其中抬高、降低幅度最大的月份分别为3月、10月，三峡建库前后对年最高水位无明显影响，建库后年最低水位出现时间明显提前、水位值明显抬高。该成果可为流域水旱灾害防御、水资源利用等方面提供基础规律支撑。

Abstract: Dongting Lake is an important large-scale lake that can regulate and store water of Changjiang River, with outstanding flood control and ecological function. This article uses mathematical statistical methods such as moving average and Mann-Kendall trend test to analyze the changes in hydrological regime of Dongting Lake before and after the operation of the Three Gorges Reservoir. The results show that the runoff in the three outlets along Jingjiang River significantly decreased by 44% after the operation of the Three Gorges, but the runoff of the four branches of Dongting Lake unchanged. The proportion of the runoff of the four branches to the total runoff of Dongting Lake increased and the proportion of the three outlets along Jingjiang River obviously decreased. The outflow of the Dongting Lake showed a significant downward trend, which decreased by 12.8% after the operation of the reservoir, mainly due to the decrease in the three outlets along Jingjiang River. From the analysis of the characteristic water level changes at Qilishan Station, a representative station in Dongting Lake, there is a significant upward trend between annual and decadal water levels. After the operation of the reservoir, the average water level at Qilishan station has risen by 0.18 meters, and the monthly average water level has the characteristics of rising before the flood season and falling after the flood season. The months with the largest degree of rise and fall are March and October, respectively. The operation of the reservoir has no significant impact on the annual highest water level. After the operation, the occurrence time of the annual minimum water level is significantly earlier, and the water level value rises. This conclusion can provide basic technical support for the prevention of water and drought disasters and the utilization of water resources in the Yangtze River Basin.