The impacts of water diversion on hydrodynamic regulation of plain river network

Abstract

平原河网多存在河道流动性不强，河道生态流速难以保障的问题，以典型平原河网地区——宁波市海曙区为例，开展野外原型同步监测，以河道分流比、换水率及槽蓄量为研究对象，系统分析引调水工程对河网水动力的调控效果.结果表明：平原河网水动力改善效果与引排水口分布、引水流量密切相关，为保证河网区水体交换良好，引排水口的连线应尽可能贯通整个区域；平原河网换水率在空间分布上具有很强的异质性（4种调水方案下河道换水率极差，最大为190%，最小为75%），引调水工程能够改善分流能力大的支汊的水动力特征，对分流能力小的支汊及断头河的水动力状况帮助不大；河网换水率提高、槽蓄量变化率减小是区域水动力改善的必要条件，海曙区较小的槽蓄量变化率为0.2%左右.本研究分析了河网区的河道输水能力以及换水率，对优化河网概化密度以减小模拟偏差有参考意义，为进一步探究平原河网水动力改善促进水环境质量提升提供基础，利于特殊水动力特征河道治理和区域水环境管控.;In the plain river network area, the mobility of rivers is usually poor and the ecological flow velocity of rivers is difficult to be guaranteed. Taking Haishu District of Ningbo City, a typical plain river network area, as an example, a field prototype synchronous monitoring experiment was carried out. The effect of water diversion on hydrodynamic regulation was systematically studied with the river diversion ratio, water exchange rate and storage capacity as the research objects. The results showed that:The hydrodynamic improvement effect of plain river network was closely related to the position of water inlets and outlets and water diversion flow. To ensure a good water exchange rate, the connection of water inlets and outlets should run through the whole area as far as possible. The water exchange rate of plain river network area had strong heterogeneity in spatial distribution (under the four schemes, the maximum range of water exchange rate was 190% and the minimum was 75%). The water diversion project could improve the hydrodynamic characteristics of the branches with large diversion capacity, but it was not helpful for the branches with small diversion capacity and truncated creek. The improvement of regional hydrodynamic needed to increase the water exchange rate and decrease the change rate of storage capacity, the smaller change rate of storage capacity in Haishu district was about 0.2%. The study analyzed the water conveyance capacity and water exchange rate, which has reference value for optimizing the generalized density of river network to reduce the simulation deviation and provides a basis for exploring the improvement of water dynamics in plain river network and promoting the water environment quality. It will also be conducive to river regulation with special hydrodynamic characteristics and regional water environment control.