Changes in land use have an impact on changes in renewable water resources. Land use especially in the context of urbanization has been and continues to be widely studied. The role of the forests in ecosystems is well known but there is not much research investigating the impact of natural afforestation on water resources. This paper shows the results of the quantitative changes in the use of the lowland catchment in the last 50 years on the example of the Zagożdżonka river located in central Poland. The results show that the impact of climatic factors on the reduction of water resources in the Zagożdżonka catchment is compounded by socio-economic changes in agriculture, and the positive role of forest areas in the catchment depends on the water demand of the stand. The interactions between forest ecosystems and water retention are strong and, depending on the habitat conditions, they may reduce ground runoff and deepen the water deficit in the catchment area in dry periods.