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PL
Budowa Zbiornika Trzech Przełomów jest największą i najdroższą inwestycją w elektrownię wodną na świecie. Jak zawsze w przypadku budowy dużych zapór, zyski i straty są istotne. Zyski nie ograniczają się jedynie do finansowych, gdyż elektrownia dostarcza dziesięć procent energii elektrycznej dla Chin, co pozwala na znaczne zmniejszenie emisji gazów ze spalania węgla ze wszystkimi tego pozytywnymi skutkami dla środowiska. Oprócz tego, zbiornik pozwolił na: kontrolę zjawisk powodziowych, poprawę żeglowności środkowego odcinka rzeki Yangtze i ujść dopływów, magazynowanie wody i zaopatrzenie w nią w okresach susz, oraz na zwiększenie zatrudnienia w rejonie zbiornika. Z kolei negatywne konsekwencje dotyczą między innymi: bardzo istotnych ograniczeń w biodywersyfikacji w rzece Yangtze, eutrofizacji wód tej rzeki i ujść jej dopływów, przesiedleń ludności na dużą skalę, zniszczenia siedlisk różnorodnych zwierząt, trudności w ochronie delty rzeki Yangtze i innych. W pracy zostały przedstawione wybrane zagadnienia związane z budową i eksploatacją tego zbiornika.
EN
Constructing of the Three Gorges Reservoir has been the largest and the most expensive investment into a hydroelectric plant in the whole World. As always in the case of building large dams benefits and losses are significant. The benefits are not only limited to income from selling electric energy but include : significant reduction of burning coal with all environmental impacts, flood control, improvements in water transportation, better water supply during dry periods, and job creation in neighbourhood of the reservoir. Negative consequences include among other things crucial effects on biodiversity in the Yangtze River, eutrophication of water in the reservoir and in the tributaries, displacement of human population, destroying of precious habitats of many species, problems with protecting of the Yangtze River delta and others. Selected economical and environmental aspects of the Three Gorges Reservoir have been described.
EN
In this study, the comparative effects of the two disturbances (aquaculture and water level fluctuations) on macroinvertebrate communities were explored in two waterbodies connected with the reservoir system of Three Gorges Reservoir (TGR) in China. One water body called Gaoyang Bay which suffered organic pollution from intensive aquaculture. Another named Hanfeng Lake, where the effects of water-level fluctuations are obvious. The results showed that aquaculture could significantly affect the chemical forms of nutrients, decrease the α-diversity and increase the β-diversity of macroinvertebrates although the communities in the treatment area in Gaoyang Bay were not fundamentally changed comparing to the control area in the same bay. The densities of macroinvertebrates in the treatment area were significantly lower than that of the control area. The composition of functional feeding groups in the treatment area was close to that in Hanfeng Lake, but obviously different from that in the control area in Gaoyang Bay and the collectors and predators dominated the communities in this control area with the highest percentages. Although water-level fluctuations had negative effects on the communities by decreasing the α-diversity and increasing the β-diversity, which were confirmed by the values of Simpson index, Shannon-Wiener index and Harrison's index in the control area of Gaoyang bay and Hanfeng Lake, the adverse effects were relative low compared to aquaculture. In the bays of TGR, the small-scale disturbance (aquaculture activities) had more significant negative effects compared to the big-scale disturbance (water-level fluctuations related to dam operation of TGR).
EN
Xanthium sibiricum, an annual weed, unexpectedly and dramatically occupied the exposed drawdown area after water had been impounded for the first time in the newly created Three Gorges Reservoir in China. In order to explain this phenomenon and establish an appropriate management strategy, the effects of constant submersion on seed viability and germination of X. sibiricum were investigated at two constant temperature regimes (25°C and 30°C) under artificial laboratory conditions. The results indicated that the seeds of X. sibiricum exhibited a high level of tolerance of submersion and up to 99% of seeds were viable in each treatment regime. The effect of submersion on germination was not obvious at 25°C until the submersion was prolonged for 180 days, while at 30°C the eventual germination rate of X. sibiricum, even after submergence for only one day, was significantly improved. The speed of germination was also consistently accelerated by prolonged periods of submersion. The proportion of seeds that germinated in all treatments combined was less that 56% due to seed dimorphism, thereby providing a seed bank. We conclude that the interaction between long-term winter flooding and high temperature in summer is the major reason that X. sibiricum was able to occupy the newly exposed drawdown area in the absence of competition. These findings provided further insight into how germination strategy and reservoir water-management regime contributed to this dramatic species outbreak.
EN
The dam construction and water impoundment have extensively altered flow regime and riparian ecosystems. However, the effect of long-term winter flooding of reservoir on plants of drawdown area is poorly known. The Three Gorges Dam in China, the largest dam in the world, created a drawdown area of 348.93 km2 between 145 m and 175 m above sea level around its reservoir. The drawdown area was submerged for more than half year in winter and exposed in summer. In the summer of 2009, the vegetation of fourteen sites in the drawdown area was investigated to determine the impact of winter flooding on vascular flora and to explore flood-tolerant species for vegetation reconstruction. One hundred and seventy five species of 58 families were recorded in present work, which indicated that 55% of vascular flora species disappear or became rare. The number of perennial species decreased to 50%. Therophytes, with 87 taxa, were the dominant life form. Strictly aquatic species were rather scarce for summer drought. Mean vegetation cover in the drawdown area was more than 70%. Species richness and vegetation cover along the elevation gradient exhibited a negative pattern correlated with flooding duration. The remarkable reduction of plant richness, variation of life form composition and alternation of dominant species indicated the strong influence of long-term winter flooding on vascular flora. Cynodon dactylon and Cyperus rotundus was highly resistant to long-term winter flooding and summer drought. Eight hardwoods (Vitex negundo, Morus alba, Sapium sebiferum, Glochidion puberum, Rhus chinensis, Melia azedarach, Pterocarya stenoptera and Trema levigata) exhibited high tolerance to winter flooding and may be potential candidates for vegetation restoration.
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