Differentiation of hydrological conditions in Kostrzyneckie Rozlewisko and Cedynski Polder of the Odra valley

Water conditions of the areas lying in river valley are shaped: on the one hand, by a natural hydrological regime of the river and on the other hand, by water runoff from the land situated higher. Most frequently the land adjoining the river, periodically depressed, with different kinds of wetland, constitutes an excellent habitat for rushes, the vegetation of great natural value. These areas are also attractive for agriculture and therefore are often transformed into meadows or arable land, depending on the soil (mineral or organic). Using the area along the river for agricultural purposes requires changing their natural hydrological conditions by technical protection in the form of polders. In order to determine the changes in hydrological conditions caused by polderisation of depressions adjacent to the river in the years 2003-2005 comparative studies on two objects, reclaimed to a different extent, were conducted. Both the objects are close to each other, in the Odra valley, not far from the town Cedynia. The object "Kostrzyneckie Rozlewisko" is to a small extent drained and transformed whereas "Polder Cedynski" is comprehensively developed hydrotechnically and agriculturally. Hydrological studies included systematic monitoring of the Odra water level and the level of groundwater on each object. Study results showed to what degree and in which direction, the Odra water levels affect the dynamics of groundwater level on both the objects. In the case of "Kostrzyneckie Rozlewisko" there is a direct and highly correlated influence whereas on "Polder Cedynski" groundwater level is shaped by a drainage network connected to the Pump Station, situated in the lower part of polder, near the village Bielinek. Detailed analysis of collected hydrometric data allowed to: determine the present hydrological situation in comparison with multi-year data for both objects (time variability), the range and frequency of flooding in the case of "Kostrzynieckie Rozlewisko" and in the case of "Polder Cedynski" assess the effectiveness of area protection from inundation