东江流域下游水文情势的改变度研究

Study on hydrological regime alteration of lower reaches of Dongjiang River Basin

【目的】水利工程的修建和运行会改变流域下游的天然水文过程,造成生态影响。定量评价水利工程对流域水文过程的影响,是完善工程调度和恢复下游生态流量过程的基础。针对目前流域水文改变度研究中对水库调度的影响分析不充分的问题,提出一种新的研究思路。【方法】以广东东江流域为例,采用耦合水库调度过程的分布式水文模型,以现行水库调度方式下的流量为基础,计算并分析水库修建后和水库不同下泄流量情境下东江下游博罗站水文过程。评估在相同气象和下垫面条件下水库的修建运行对流域下游水文情势的影响程度。【结果】结果显示:(1)东江流域新丰江、枫树坝和白盆珠三大水库的修建和运行显著改变了下游博罗站的月流量过程、年极值流量以及年内径流改变率等水文指标,尤其是高低流量出现频率、流量增加率减少率和流量逆转次数改变较大;(2)新丰江单库运行阶段的整体水文改变度为70.90%,枫树坝和新丰江双库调度阶段的整体改变度为70.96%,三大水库联合调度阶段的整体水文改变度为71.77%,均属于高度改变;(3)提高上游水库的月最小下泄流量阈值,对下游的水文改变度较为明显,其中对新丰江坝下水文改变程度最显著。【结论】结果表明:分布式水文模型耦合水库调度和水文改变指标变化范围法,是评价流域水文情势变化的重要手段,对于缺少水库修建前实测径流数据的流域水文情势研究具有较大的实用价值。此外,研究建立的耦合水库调度的分布式水文模型以及水库水文改变度计算方法,可为流域多水库联合生态调度方案的制定提供技术支撑。

[Objective]The construction and operation of reservoirs will change the natural hydrological processes in the lower reaches of the river basin and cause ecological impacts.Quantitative evaluation of the impact of reservoirs on the hydrological process of the basin is the basis for improving water operations and restoring the downstream ecological flow process.Aiming at the problem of insufficient analysis of the influence of the degree of hydrological change on the reservoir operation in the current study,a new research idea is put forward.[Methods]Taking Dongjiang River Basin in Guangdong Province as an example,the distributed hydrological model coupled with reservoir dispatching process is adopted to calculate and analyze the hydrological process of Boluo Station in the lower reaches of the Dongjiang River after the construction of the reservoir and under different discharge discharge situations based on the current reservoir dispatching mode.To evaluate the influence of the construction and operation of the reservoir on the downstream hydrological regime under the same meteorological and underlying surface conditions.[Results]The result show that the construction and operation of the three major reservoirs,Xinfengjiang,Fengshuba and Baipenzhu reservoirs in the Dongjiang River Basin,have significantly changed the monthly flow process,annual extreme flow,and annual runoff change rate of the downstream Boluo Station.In particular,the frequency of high and low flow rate,the rate of flow increase rate and decrease rate and the number of flow reversal have changed greatly.The overall hydrological change degree of Xinfengjiang single reservoir operation stage is 70.90%,the overall hydrological change degree of Fengshuba and Xinfengjiang double reservoir operation stage is 70.96%,and the overall hydrological change degree of the three reservoirs combined operation stage is 71.77%,all of which have been highly changed.The higher the monthly minimum discharge threshold of upstream reservoir,the more obvious the hydrological change degree of downstream.The hydrological change under Xinfengjiang reservior dam is the most significant.[Conclusion]The distributed hydrological model coupled with reservoir operation and the method of variation range of hydrological change index is an important means to evaluate the change of hydrological regime in a basin,and has great practical value for the study of hydrological regime in a basin that lacks measured runoff data before the construction of a reservoir.In addition,The distributed hydrological model of coupled reservoir scheduling and the calculation method of reservoir hydrological variation can provide technical support for the formulation of multi-reservoir joint ecological scheduling scheme.