水库调蓄对通江湖泊四大家鱼繁育-洄游循环过程的影响研究

Four major chinese carps are spawning in the Yangtze River Mainstream, growing in the lakes connecting with the River, so the changes of the relationship between the River and Lake is closed to the breeding of the carps. Domestic research focused on the hydrological regime changes of the River and Lake caused by the running of the Three Gorges Reservoir, which would influence the breeding of the carps, such researches mostly are based on single background, River or Lake, but the River and Lake are connect with each other ,that would make the hydrological regime change together, so based on the relationship between the River and Lake, how the River Mainstream water rising would change effected by the water diversions, and then the changes might effect the spawning of the four major chinese carps, and the meanwhile, the lake outlet water level might effect the migration of the carps, those above are studied less up to now. In this idea, long term water rising in the Yangtze River Mainstream which is closed to the spawning of the carps should be analyzed first, based on analyzing of the characteristic that three diversion flow changing along with the flow change of the Jingjiang River, the weakening of the different water rising caused by the three diversion should by studied, the analyzing the optimal flow process of the Three Gorges Reservoir to the carps by using the reservoir dispatching system, building the relationships between the water level at the lake outlet in the flood period and numbers of the carps which are migrating into the lake by analyzing the measured data and the mathematic model.

长江中游四大家鱼于干流繁殖、湖内育肥，江湖分汇与家鱼繁育关系密切。国内学者针对三峡水库径流调节作用改变江、湖水文情势影响鱼类繁育进行了一定的研究，相关研究大多单独以江或湖为背景分析与鱼类相关的水文过程变化，而以江湖分汇关系为基础综合研究：分流作用下干流涨水特征影响鱼类产卵、汇流作用下湖口的水位变化影响鱼类洄游，相对较少。本项目首先分析长江中游重点产卵江段与家鱼产卵密切相关的涨水过程长系列变化情况，再通过分析荆江三口分流能力随干流流量的变化特性，研究三口分流对不同涨水过程的削弱程度，结合水库调度模型，分析三峡水库针对下游鱼类产卵的最优生态放水过程；分析洞庭湖湖口汛期水位变化特点与鱼类洄游的关系，利用数学模型模拟三峡水库不同调蓄方式下洞庭湖出口水位变化，与鱼类洄游数量及种类建立关系。本研究对认识水库径流调节作用对下游河湖域内鱼类繁育的影响有重要理论意义，为制定科学合理的水库调度提供技术支撑。

本项目基于长江荆江段干流与三口分流洪道多年径流资料，分析干流径流量与三口分流量长系列变化情况，结合干流河道与三口洪道冲淤变化，研究了三峡水库运行对荆江三口分流的影响，结果表明：三峡水库蓄水后，由于荆江干流中高流量对应三口分流比变化不大，故荆江三口分流量减少，是由干流中高流量持续时间的减少引起，而干流中高流量持续时间的减少一方面是蓄水后多年小水导致长江干流自身径流量偏小，另一方面则是三峡水库的调蓄作用改变荆江干流径流过程。因此，在考虑荆江三口分流对干流涨水过程影响时，不需要考虑洪道冲淤对三口分流能力的影响。基于金沙江及荆江河段四大家鱼早期资源监测资料，以及长江干流宜昌水文站长系列水文资料，通过定义与四大家鱼亲鱼产卵繁育密切相关的高流量脉冲过程，即日流量高于70%的流量为高流量，流量频率范围在45%-70%之间时，日流量涨幅超过15%，则高流量脉冲开始，直到某天下降超过10%结束，进一步研究了四大家鱼与干流5月至8月出现首次及后续多次高流量脉冲之间的相关性，得到以下结论：（1）根据目前掌握的2010-2016的鱼类产卵监测资料，分析了每年第一次高流量脉冲期间的四大家鱼产卵情况，可见所有第一次高流量脉冲期间都发生了四大家鱼产卵，说明四大家鱼对每年进入五月的第一次高流量脉冲较为敏感；（2）2010-2016年，24次高流量脉冲过程中，有21次观测到了四大家鱼产卵，表现出很高的相关性，四大家鱼产卵行为与高流量脉冲的相关程度可能高于其与涨水过程的相关性，在高流量脉冲信号出现后的脉冲期，即使出现一定程度的落水，脉冲信号的持续刺激，仍可能让家鱼出现产卵行为，这与以往研究中讨论的，一旦出现流量回落，产漂流性卵鱼立刻停止产卵的结论略有不同，需要进一步研究。根据以上结论，首次脉冲与四大家鱼年内产卵与否、产卵规模关系极为密切，且与三峡水库生态调度时期吻合，因此分析宜昌流量特征，并根据高流量脉冲水文特点，给出了调度建议。