The amount of water required to support a river ecosystem in proper condition are of particular importance in the areas of high natural value. The hydrological threats for the protected areas are region-specific and vary from region to region. The local hydrological conditions depend largely on the temporal and spatial variations of the hydrologic cycle, of the main components and physiographic conditions on site. Future climate change is projected to have a significant impact on the hydrological regime, water resources and their quality in many parts of the world. The water-dependent ecosystems are exposed to the risk of climate change through altered precipitation and evaporation. Investigating the current climate changes and their hydrological consequences are very important for hydrological issues. This analysis may be a very important foundation for determining the causes observed in the recent period of anomalous growth – both hydrological and climatic. The aim of the research is to assess the effect of projected climate change on water resources in lowland catchment the Narew River in Poland. The hydrological reaction to climate warming and wetter conditions includes changes in flow and water level. This paper describes the directions of changes climatic and hydrological conditions and the impact of climate change on the Narew River. The data such as: daily air temperature, precipitation obtained from the Bialystok climate station located within the Narew river and hydrological data such as water flows and water states observed in water gauges were used for the analysis of climate variability and their hydrological consequences. The results show a significant decrease in winter outflows in river, as well as a delayed increase in the spring melt flow. It has also been observed that this is the initial phase of changes in maximum water levels and maximum flows.