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Abstract

Floodplains with high degrees of hydrological connectivity usually have high biodiversity and provide a wide range of ecosystem services (flood protection). It is crucial to understand how, where and for how long floodplain wetlands store water; where and when this water is released, and what the implications are for water availability and quality. We considered controls on the spatio-temporal extent of floodplain inundation on the extensive wetlands of the Lower Oder Valley National Park, NE Germany. The floodplains have been managed as controlled polder systems since 1990. The wetlands are highly sensitive to changes in connectivity with the River Oder. We assessed the influence of climatological and hydrological variables, land use, soil type and topography on the variability of the water surface area. We combined long-term hydrometric data with different environmental tracers to quantify sources, pathways and ages of waters via spatially distributed sampling. Through continuous wavelet transformation the spatial-temporal variation of the water surface area was investigated, and wavelet coherencies were calculated to understand periodicity in water surface area signals. Landscape characteristics, climatic signals, water levels of the Oder, subsurface water storage, and water insight polders were analysed to illustrate how these variables control the inundated area. Strong non-stationary behavior of water surface area inside the polders across multiple time-scales was identified. This provides important science-based evidence for the National Park’s land and water management strategies targeted at building resilience to protect these extensive wetlands in the face of increasing climatic and other anthropogenic disturbances.