Changes in runoff as an indicative measure of water retention status in the Białowie˝a Primeval Forest

The study concerned changing status of water retention within an unique nature complex of the Białowieża Primeval Forest. The retention was evaluated based on an analysis of research results on water outflow from the lowland catchment of the river Łutownia - representative for physiographic conditions as well as those of habitats and tree stands in Poland’s part of the Forest. The catchment in the lowland hydrometric dissection at the Pogorzelce village - Old Białowieża Wilderness, covers the area of 120.1 km2 with natural flow conditions preserved. A unified sequence of measurements carried out since 1966 using unchanged methodology with respect to precipitation, air temperature and forest management status allowed to separate different phases of changes occurring in water resources of this protected forest complex. There were appraised periodical runoff changes and cycles including a decrease in water resources which occurred at the turn of the century. The retention capacity of the catchment was determined based on periodical changes in rainfall-runoff relations and the ongoing process of deteriorating water conditions of forest ecosystem was interpreted.