In the beginning of the 20th century the - until then, largely undeveloped - Oder Valley was transformed according to Dutch plans. The objective was to enable year round, large freight barge traffic on the route Berlin – Stettin (Szczecin), to improve agricultural yields in the river valley and to prevent flooding further South. On that occasion several wet polders (Polder A: 1644 hectares, Polder B: 1303 hectares, Polder 10: 1773 hectares) were created on what today is the German side. These wet polders are polders protected by dikes, which are located between the Oder stream in the East and the Hohensaaten-Friedrichstal-Canal in the West. The former Gartz-Polders and the Schillersdorf-Polders, which are now in Poland were designed as wet polders as well.
Normally the polders are only submerged in the winter. However, beginning on the 15th of April of every year they are dried up through natural drainage as well as with the help of electrical pumps. Conservation plans intend to restrain human influence on the flood dynamics on the wet polders, and to leave open the floodgates year round, or at least until May 31st of each year.
For a riparian national park specifically, it is essential to keep water conditions as natural as possible. A provincially funded feasibility study focusing on water management came to the conclusion that with certain restrictions on agriculture, such a year round opening of floodgates is possible at least for the Fiddichow-Polders (10), but technically also for the Criewen- and Schwedt-Polders (A/B), with no curtailment of disaster flood protection.
Twelve years after foundation of the National Park at least the small, 40 hectare Staffeld-Polder (8) has been reconnected to the dynamics of the Western Oder. To that end the dike that separates the polders from the Western Oder, was opened in three spots in 2008. The Western Oder, however, is not a natural body of water, and gets only a limited amount of water from the actual Oder stream according to specific rules through the floodgates at Marienhof. Aside from that, the Western Oder is connected to the water system of the Hohensaaten-Friedrichsthal-Canal, is at sea level, and its flow is strongly influenced by the Szczecin Lagoon and the Baltic Sea.