长沙枢纽枯水期下游超设计低水位运行的影响及对策

Influence and countermeasures of lower reaches of Changsha Hub operation below design low water level in dry season

长沙枢纽枯水期下游尾水位出现远低于设计最低水位的情况。为了分析其影响和研究对策,采取数据统计分析等方法,从下游低水位以及对应的水头参数对枢纽大坝运行、船闸通航、电站运行的影响进行综合分析,并提出以下对策:大坝原最大工作水头9.3 m提升至11.2 m;通过枢纽短时调度和流域联合调度保障最低生态流量348 m3/s;采取“分段、划区、有序、控时、限量”综合管控下游河道采砂;采取“多孔数,少流量”泄水,定期水下摄像和大坝安全监测确保大坝安全;防止船舶搁浅,采取“先慢后快”方式开启船闸输水阀门,确保浮式系船柱“磕底”时系缆安全,修建3 000吨级三线船闸,确保船闸通航安全;机组在水头7.0 m以下运行,下游水位低于19.55 m时禁止开机,及时进行电站前池清淤,确保电站运行安全。

The downstream tail water level of Changsha Hub is far lower than the designed minimum water level in the dry season.In order to analyze its impact and study countermeasures,this paper adopts methods such as data statistics and analysis,comprehensively analyzes the impact of downstream low water level and corresponding water head parameters on the operation of the hub dam,navigation of the ship lock and operation of the power station,and proposes countermeasures as follow.The original maximum working head of the dam should be raised from 9.3 m to 11.2 m.The minimum ecological flow of 348 m 3 s should be ensured through hub short-term dispatching and basin joint dispatching.“Segmentation,zoning,orderliness,time control,and quantity limit”should be adopted to comprehensively control sand mining in the downstream river channel.“More holes and less flow”should be adopted to release water,and underwater photography and dam safety monitoring should be adopted regularly to ensure dam safety.To prevent the ship from stranding,the water conveyance valve of the ship lock should be opened in a way of“first slow and then fast”to ensure the safety of the mooring line when the floating bollard hits the bottom.A 3000-ton three-line ship lock should be built to ensure the safe navigation of the ship lock.The unit should operate under the operating water head of 7.0 m,and the unit should not be started when the downstream water level is lower than 19.55 m.The forebay of the power station should be cleaned in time to ensure the safe operation of the power station.