Patterns of low-flow and zero-flow events in Polish rivers: climate signal or catchment impact?

Climate change is an obvious driver of changes in water regimes in Polish rivers. However, human interventions in catchments strongly magnify its negative effects. One of the most visible consequences is the increasing intermittence of rivers that only a few years ago flowed throughout the year. In Poland, river intermittence is a relatively new phenomenon. Smaller rivers now disappear for significant parts of the year due to prolonged hydrological droughts.

Within the project “Intermittent rivers of Central Europe: Identifying threats to protection goals and biodiversity for efficient nature conservation and climate-proof environmental management”, we analysed all available Polish records of daily discharges and identified 22 gauging stations where extremely low or zero flow occurred at least once during the observation period.

We observed strong temporal unevenness in the occurrence of low-flow events, suggesting that gradual climatic change alone may not fully explain the development of river intermittence. Indeed, when compared with land-cover changes derived from successive CORINE Land Cover maps, some stations revealed sudden increases or decreases in the frequency of low-water events. Although this pattern was not observed for all analysed intermittent rivers, it may provide further evidence that unsustainable water management practices in catchments amplify the effects of climate change.