The diagram compares how the water cycle operates in forested areas and urban environments, highlighting differences in infiltration, evaporation, runoff, and groundwater recharge.
Overall, natural forested landscapes allow a substantial proportion of rainfall to infiltrate the soil and replenish underground water reserves, whereas urban surfaces significantly reduce infiltration and increase surface runoff, leading to greater erosion and pollution.
In forested regions, precipitation falls onto permeable topsoil, enabling a large share of water to seep downward through the soil layers and into the water table. Some of this water later returns to the surface through the baseflow, sustaining rivers and streams. At the same time, vegetation plays an important role in returning moisture to the atmosphere: trees absorb water through their roots and release it via transpiration, while evaporation also occurs from the ground surface. As a result, runoff is relatively limited in such natural settings.
By contrast, in urban areas, impermeable surfaces such as roads and buildings restrict the ability of rainwater to infiltrate the ground. Consequently, infiltration and groundwater recharge are reduced, while surface runoff increases markedly. This runoff often carries pollutants and contributes to greater erosion. In addition, the reduced presence of vegetation leads to lower levels of transpiration and evaporation, further altering the natural balance of the water cycle.
In summary, forested environments promote groundwater replenishment and balanced water circulation, whereas urban development disrupts these processes by intensifying runoff and reducing infiltration.