Due to human impacts, floodplains in urban regions are often simultaneously affected by eutrophication, loss of hydrological dynamics and even land use change. In order to mitigate some of these effects in a degraded floodplain within the city limits of Vienna, the "Dotation Lobau" a water enhancement scheme, was initiated in 2001. The present contribution demonstrates the effects of surface reconnection, with a low discharge (mean 0.2 m 3 s -1 ), on the phosphorus budget, by comparing connected and isolated backwaters. The surface water supply resulted in a decrease of mean trophic levels due to a decreased hydrological retention time and the establishment of a transport phase (phosphorus output). Furthermore, the study indicated that primarily sediment-associated processes, such as the accumulation or release of phosphorus, will influence the long term development of the floodplain.