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This paper presents past and recent water management in the area called the Vistula Delta Fens (Żuławy Fens). This area (56 x 56 km) is located at the outlet of the Vistula River to the Baltic Sea, at the shore of the Gulf of Gdańsk. A large part of the area (30%) is located below sea level as potentially submerged depressions. A multitude of rivers, channels, ditches and pumping stations have been constructed here over several centuries. The area is characterized by highly productive alluvial soils, surface water with a high potential for fish-farming and fishery, and attractive tourist areas at the banks of the rivers and channels. Historically, floods have occurred repeatedly as a result of: (i) – breaks in the dams along big rivers, e.g. after heavy rains and high water levels (in summer); (ii) – dam breaks caused by accumulation of ice-cakes in winter or during spring times; (iii) – dam breaks after storms on the sea with increasing sea water levels at the river outlets (mainly in winter); (iv) – overflow of water into flat land after heavy rains followed by slow drainage of water from the fields, ditches, channels and pumping stations (in summer); (v) – overflow of water into depressions and swamps below sea level after interruptions of, or decreases in, the pump operations at the pumping stations. The EU directive on flood control advises that the member countries should: (i) – produce maps of the areas vulnerable to floods to facilitate communication and planning; (ii) – develop management plans for flooding events; (iii) – exchange experience and codes of good practice during flood; (iv) – facilitate a close cooperation between the scientific community and politicians in the field of flood protection; (v) – raise the level of knowledge, communication and awareness among local societies living in areas prone to flooding.
The Salix variegata Franch. seedlings planted in the Three Gorges Reservoir (TGR) water level fluctuation zone (WLFZ) could survive after experiencing several seasons of winter submergence. We investigated the recovery mechanisms of S. variegata seedlings planted at the elevation of 168 m and 172 m in the TGR WLFZ after winter submergence. The results indicated that winter submergence caused some impacts on S. variegata seedlings with increases of hydrogen peroxide (H₂O₂), superoxide anions radical (O₂⁻˙), and malondialdehyde (MDA) levels, and decreases of antioxidant enzymatic systems during recovery stage after winter submergence. However, further analyses of relative water content (RWC), pigment content, proline content, carbohydrate content and several other antioxidant enzymatic activities (catalase (CAT), guaiacol peroxidase (G-POD), and glutathione peroxidase (GSH-POD)) showed that S. variegata seedlings were well recovered after winter submergence. These results indicate that S. variegata possesses strong winter submergence tolerance and adaptation to the specific hydrological environment in the TGR WLFZ. Therefore, S. variegata should be popularized as native tree species during the revegetation in the TGR WLFZ.
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