赣江尾闾多级分汊河道水动力空间优化研究

Study on hydrodynamic spatial optimization of multi-level branched channels in Ganjiang River estuary

摘要

【目的】针对赣江尾闾河段因水动力分配不均导致的航运受阻、生态退化等衍生问题，拟通过定量分析南昌水利枢纽蓄水运行后的分流比优化方案，改善尾闾河段水动力分配不均问题。【方法】基于水动力数值模拟方法，构建了赣江尾闾河段二维水动力模型。模拟1983—2018年四种历史分流比工况下枢纽蓄水至外洲站水位15.5 m时的水动力响应特征，分析各分支河道流速变化规律；结合尾闾河段航运、生态流量要求、流速需求与各支过流能力，明确水量分配多目标约束条件；采用最大化最小流速法(Max-Min准则)进行分流比优化。【结果】研究表明：在枢纽蓄水后，在外洲流量小于等于2 000 m³/s,外洲与下游各支闸前的水位落差在0.5 m以内，且流量越低落差越小；优化后的分流比方案在外洲流量500 m³/s时，较四种历史分流比方案将各支流速下限提高了18.9%以上；1 000 m³/s时将流速下限提升了12.3%以上；2 000 m³/s时将各支流速下限提升了15.4%以上，控制在0.16~0.19 m/s避免了其他分流比方案产生的流速极端差异；4 000 m³/s时降低了流速的上限，使得各支流速在0.46 m/s以下，较其他分流比缓解了高流速对河床的冲刷。【结论】通过南昌枢纽的流量调控，可以有效改善各支水动力的不均匀特性，在各支流水动力满足基本的生态、航运需求的基础上提升了流速下限，控制了流速上限，解决了支流季节性断流问题，为多目标协同的水资源调度提供决策依据。

Abstract

[Objective] The issues of navigation obstruction and ecological degradation are caused by uneven hydrodynamic distribution in the river section of the Ganjiang River estuary. To address these, the optimization of flow diversion ratios after the impoundment operation of the Nanchang Hydraulic Hub is quantitatively analyzed, thereby improving the uneven hydrodynamic distribution in the river section of the estuary. [Methods] Based on hydrodynamic numerical simulation, a two-dimensional hydrodynamic model of the river section of Ganjiang River estuary was established. The hydrodynamic response characteristics were simulated under four operating conditions of historical flow diversion ratios from 1983 to 2018 when the hub impoundment raised the water level at Waizhou station to 15.5 m. The flow velocity variation patterns in each channel were analyzed. Combining navigation requirements, ecological flow demands, flow velocity requirements, and the flow capacity of each branch in the river section of the estuary, multi-objective constraints for water allocation were defined. The Max-Min criterion(maximization of minimum velocity method) was applied to optimize the flow diversion ratios. [Results] The result showed that after the hub impoundment, when the flow at Waizhou station was less than or equal to 2 000 m³/s, the water level difference between Waizhou and the downstream gates of each branch remained within 0.5 m, with smaller differences observed at lower flow rates. Under the optimized flow diversion ratio scheme, when the flow rate at Waizhou station was 500 m³/s, the minimum flow velocity in each branch increased by over 18.9% compared to the four historical flow diversion schemes. At 1 000 m³/s, the lower limit of flow velocity increased by more than 12.3%. At 2 000 m³/s, the lower limit of flow velocity in each branch increased by more than 15.4%, maintaining velocities within the range of 0.16 to 0.19 m/s and avoiding extreme flow velocity differences caused by other flow diversion ratio schemes. When the flow reached 4 000 m³/s, the upper limit of flow velocity reduced, keeping the velocities of all branches below 0.46 m/s, thereby alleviating the scouring of riverbeds caused by high flow velocity compared to other schemes. [Conclusion] Flow regulation via the Nanchang Hub effectively improves the uneven hydrodynamic characteristics among the branches. While meeting the basic ecological and navigation requirements of each branch, this regulation raises the lower limit of flow velocity, controls the upper limit, and addresses the issue of seasonal flow interruptions in the branches, thereby providing a decision-making basis for multi-objective coordinated water resource scheduling.

关键词

赣江尾闾 / 数值模拟 / 多级分汊河道 / 多目标优化 / 水动力 / 鄱阳湖

Key words

Ganjiang River estuary / numerical simulation / multi-level branched channels / multi-objective optimization / hydrodynamics / Poyang Lake

基金资助

国家重点研发计划项目“长江中下游平原河网区水动力优化再构与自然动能高效利用”(2022YFC3202603)

江西省水利厅科技项目“入湖多级分汊河道多目标流量动态调控技术研发与应用”(202325ZDKT04)