三峡水库富营养化问题与对策研究

三峡水库蓄水后,大部分库湾已出现富营养化态势,并暴发了数次以甲藻(拟多甲藻)和硅藻(小环藻)为主的水华现象,特别是在春季。以香溪河库湾为例,分析两周年的营养状态变化,总体上说,除冬季外,大多数月份为富营养,在春季则为重富营养。对三峡水库22条入库支流库湾的营养状态进行综合评价,结果表明,有5条(22.7%)支流库湾为中营养,17条(77.3%)支流库湾为富营养(重富营养化支流库湾有10条,占45.5%);但三峡水库本身水质尚好,仍保持中营养状态。统计分析表明,入库支流流域的年均流量和流域面积与支流库湾叶绿素a存在显著负相关关系,说明支流库湾越小或年均流量越小,藻类叶绿素a浓度就越高,即越容易在春季形成水华。文中讨论了控制和减缓富营养化几项措施。

Studies on eutrophication problem and control strategy in the Three Gorges Reservoir

On 1st June 2003,the Three Gorges Reservoir(TGR) began its storage officially, and the water level reached at 135 m on 10 June(and at 139 m on 5 November).Three are a lot of tributaries been flooded in the lower reaches,and many bays are therefore formed from that time in the reservoir.We monitored the changes of ecological environment of TGR,and found that most of bays was in eutrophic state and emerged several serious algal blooms predominated by dinoflagellate(Peridiniopsis spp.) and diatom(Cyclotella sp.),especially in spring.In case of Xiangxi Bay,the largest one in Hubei part of TGR and the one most close to the dam,the monthly monitoring of 2 years shown that the trophic state in most month was eutrophic,except in winter.Farthermore,the trophic state in spring was hyper-eutrophic.On the other hand,to get a general information of eutrophication situation in TGR,we assessed the trophic state of 22 bays and TGR itself in spring,2005.The results shown that 5 bays(22.7%) were in meso-trophic,and 17 bays(77.3%) were in eutrophic(10 bays in hyper-trophic,occupied 45.5%).The water quality of TGR itself,however,was still in good condition(meso-trophic),due to its fast exchange rate of water.Statistic analyses shown that relationship between chlorophyll a and watershed characters(annual discharge and catchment area) of bays in TGR was significant negative.It implied that,generally,the smaller of the bay(or its annual discharge),the higher of chlorophyll a concentration,i.e.the easier of forming algal bloom in spring.Based on the monitoring and researching,we discussed and proposed several strategies to control or mitigate eutrophication phenomena in TGR,including pollution control,complete survey,mechanism study and eco-hydraulic regulation.