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 river – floodplain interaction was 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 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.