On the role of water balance as a prerequisite for aquatic and wetland ecosystems management: A case study of the Biebrza catchment, Poland

Water balance quantifies the inflows and outflows in a river basin, crucial for assessing the water resources of a given area. Quantified water balance should therefore be the key step in environmental quality assessment. However, due to the lack of data on reasonable spatiotemporal scales and quality, water balance studies are scarce. The aim of the paper was to provide a water balance analysis as a prerequisite for aquatic and wetland ecosystems management in the Biebrza Valley, Poland. A Penck-Oppokov method was used to assess the annual water balance, and runoff coefficient for 1951–2021. Data were extracted for the daily simulated dataset of Poland. The average annual water balance of the Biebrza basin encompassed of 561 mm of precipitation, 485 mm of evapotranspiration, 101 mm of runoff, and −25 mm of water retention. Analysis of 17 sub-basins indicated a declining tendency in water resources over the study period. The average runoff coefficient in the Biebrza basins is equal to 0.17. Findings presented here indicate that the significant deficit in the water balance in the region is highly unlikely to be compensated by the course of natural hydrological processes. This reveals the need for quick actions oriented at improvement of water balance by reducing the runoff and evapotranspiration. The study provides convincing evidence that if the observed tendencies of water balance elements are continued, the reinstallation of spatially distributed, abundant measures of increasing water retention may be the only way to assure the appropriate ecological status of aquatic and wetland ecosystems.