Over the last twenty years, the number of projects aimed at river restoration and rehabilitation increased significantly. In the city it is impossible to provide full river restoration, but at the same time it is possible to create a comfortable natural environment both for flora and fauna and for the citizens. In our work it was assessed the possibility of the floodplain restoration by the water replenishment of the dry old riverbed during the vegetation season on the example of the river inside the city. The simulation of the current state allowed to verify the main parameters of the model with the existing observations of the water levels in the river and lake and water levels in the wells located in the park. The several models of the river -floodplain interaction were simulated: floodplain was separated from the river by the flood control dyke, the water replenishment of the lake and the old riverbed was due to seepage (current state); the connection of the floodplain with the river by the culvert and the replenishment of the lake and the old riverbed with surface river water. The simulation showed that the lake isolated from the river is filled to a depth of not more than 0.5 m, the old riverbed is filled with water only during spring floods. The water balance calculations of the lake showed that in the conditions of isolation from the river, the lake volume is significantly affected by precipitation and evaporation from the lake water surface area. The connection of the lake with the river surface water significantly reduces the impact of the vertical components of the water balance, at the same time increases the seepage losses from the lake because of the water level raising. The connection of the river with the floodplain makes it possible to replenish the old riverbed and the lake in the mean year, but in the dry years the water level in the lake does not allow to replenish the old riverbed during the vegetation season. Calculations showed that to be able to keep the constant water level in the lake and old riverbed, it is necessary to increase the water level in the lake.

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One of the tasks in modern approach of the water resources management is improving environment health by the way of the river restoration. On the urban area it is impossible to provide full river restoration, but at the same time it is possible to create the environment close to natural. In our work on the example of the river Uzh located inside the city provides the assessment of the restoring possibility of the part of the floodplain by water replenishment of the old riverbed during the vegetation season. Flood control dyke construction interrupted the connection between old riverbed and river and as a result floodplain lake became muddy, silted up and lost its attractive form. To assess the possibility of the floodplain lake replenishment, the simulation of some scenarios were carried out: natural condition, water replenishment during flood, pumping water, raising water level in the river Uzh near the lake. The connection of the lake and the old riverbed with the river will improve slightly the storage capacity of the lake and allows to provide the depth of up to 1.0 m in the lake during flood, but the water will be absent in the old riverbed during the dry season. Hydraulic calculation showed that replenishment during spring floods and pumping water were not possible due to high hydraulic conductivity of the gravel and pebble soils. The old riverbed replenishment is possible by raising water level in the river Uzh, which will ensure the free water flow into the lake and into the old riverbed during the dry season.

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