What is runoff?

Runoff is defined as water that flows over the ground surface. This occurs when precipitation falls and exceeds the soil's ability to absorb it, resulting in excess water flowing across the land. Runoff can carry with it nutrients, sediments, and pollutants, making it an important factor in the hydrological cycle and affecting ecosystems and water quality in bodies of water.

In contrast to processes like evaporation or infiltration, which involve water being absorbed into the atmosphere or the ground, respectively, runoff is specifically about the movement of water across the landscape. Understanding runoff is crucial for managing water resources, agriculture, and environmental conservation, as it plays a key role in erosion, water quality, and the balance of natural systems.