Final answer:
Runoff water is the flow of water that drains from saturated or impermeable surfaces into water bodies and is a part of the surface runoff process in the water cycle. It contrasts with groundwater, which is the portion of precipitation that percolates into the ground and may eventually become part of the underground water storage.
Step-by-step explanation:
Water that drains from saturated or impermeable surfaces, such as during a rainstorm, and is not absorbed by the soil is termed as runoff water. This surface runoff can be seen as water flowing over land, which then makes its way into streams and rivers, and eventually reaches larger bodies of water like lakes or the oceans. In contrast, some of the precipitation may percolate into the ground and become groundwater. This groundwater can be stored in places like aquifers, seep out into water bodies, be used by plant roots, or contribute to the flow of rivers through groundwater seepage.
During heavy rainfall or snowmelt, the soil can become saturated, leading to a higher volume of surface runoff. Runoff is readily visible, especially in urban areas with impermeable surfaces where water quickly forms streams on streets and parking lots. In natural environments, vegetation plays a role in initially intercepting rainwater.
This process, along with evapotranspiration, is crucial in the water cycle, which involves water movement through evaporation, condensation, precipitation, and infiltration. The earth's water cycle demonstrates the interaction between groundwater and surface water, both integral for supplying fresh water for various human needs, including drinking water, agriculture, industry, and recreation.