三峡水库运行对荆江三口分流的影响评估

荆江三口作为连接洞庭湖和荆江的纽带,历来是研究洞庭湖区防洪、航运、水环境变化和水资源利用的关键点。通过建立荆江三口分流模型,将2008—2015年枝城日实测流量和相应的还原流量作为模型输入资料,计算出有、无三峡工程情况下荆江三口的分流量。探讨了三峡水库对荆江三口发流量、分流比、断流情况的影响(此影响为径流调节和河道调整的综合影响),同时分离并探讨了河道调整对荆江三口分流量变化的影响。结果表明:有三峡工程情况下,在径流调节和河道地形调整的综合影响下,汛前消落期荆江三口多年平均分流量和分流比分别增大28.17%,9.59%,断流情况基本无变化;汛期多年平均分流量减少2.11%,分流比增长0.56%,断流情况变化不大;汛末蓄水期多年平均分流量和分流比分别减少33.87%和19.84%,松滋口和太平口断流情况无明显变化,藕池口断流天数增多且断流日期提前;枯水期三口多年平均分流量增大8.60%,多年平均分流比减小2.93%,松滋口和藕池口在有三峡工程情况下每年分别平均少断流30.43,6.80 d,太平口每年平均多断流30.86 d;其中,河道地形调整使汛期荆江三口分流量增加2.73%,汛前消落期、汛末蓄水期、枯水期荆江三口分流量分别减小16.62%,3.10%,18.49%。该结果可为洞庭湖区湖泊干旱情况、水资源利用与保护及三峡水库的运行调度提供研究基础。

Evaluation of the Impact of Three Gorges Reservoir on Three Outlets of Jingjiang River

The three outlets of Jingjiang river, as the link between Dongting Lake and Jingjiang River, has always been the key point of flood control, shipping, water environment changes and water resources utilization in Dongting Lake area. In this paper, the diverted flow rates from Jingjiang River in the presence and in the absence of the Three Gorges Reservoir were calculated using a flow diversion model of the three outlets of Jingjiang River. The observed and corresponding naturalized data of daily flow rate at Zhicheng station during 2008-2015 were taken as the model inputs. Moreover, the influences of the Three Gorges Reservoir on the runoff, diversion ratio and diverted flow of the three outlets (including the comprehensive influence of runoff regulation and river channel adjustment) were discussed, and in particular, the influence of river channel adjustment on the runoff of the three outlets was expounded. In the presence of the Three Gorges Project, under the comprehensive influence of runoff change and river channel topography regulation, in pre-flood season the multi-year average diverted runoff and diversion ratio increased by 28.17% and 9.59%, respectively, and the zero-flow situation of the outlets basically remained unchanged; in flood period the annual average runoff decreased by 2.11% while diversion ratio increased by 0.56%, with the zero-flow situation changed little; in post-flood season, the multi-year average diverted runoff and diversion ratio decreased by 33.87% and 19.84% respectively, with barely no change in the zero-flow situation at Songzi and Taiping whereas increased and advanced days of zero-flow at Ouchi; in dry season, the multi-year average diverted runoff increased by 8.60%, the multi-year average diversion ratio decreased by 2.93%, and the multi-year average number of days of zero decreased by 30.43 days and 6.80 days respectively at Songzi and Ouchi, but increased by 30.86 days at Taiping. In addition, the adjustment of river channel topography increased the runoff of Jingjiang River by 2.73% in flood season, and reduced the runoff of Jingjiang River by 16.62%, 3.10%, and 18.49% respectively in pre-flood season, pre-flood season and dry season. The research findings lay a foundation for the study of lake drought and water resources utilization and protection in the Dongting Lake area as well as the operation of Three Gorges Reservoir.