Runoff

Definition

Runoff refers to the water that flows over the surface of the ground after precipitation, rather than being absorbed into the soil. This water can originate from rain, melted snow, or ice and is an essential part of the hydrologic cycle as it contributes to rivers, lakes, and oceans. Runoff plays a critical role in transporting nutrients and sediments, influencing water quality and ecosystems along its path.

5 Must Know Facts For Your Next Test

1. Runoff occurs when precipitation exceeds the rate at which the ground can absorb water, leading to excess water flowing over the surface.
2. Urbanization can significantly increase runoff due to impervious surfaces like roads and buildings, which prevent water infiltration into the ground.
3. Runoff can carry pollutants from urban areas, agricultural fields, and industrial sites into bodies of water, affecting water quality and ecosystems.
4. There are two types of runoff: surface runoff, which flows over the ground, and subsurface runoff, which occurs below the surface through soil layers.
5. Managing runoff is important for flood control, erosion prevention, and maintaining water quality in rivers and lakes.

Review Questions

• How does runoff impact the hydrologic cycle and what factors influence its occurrence?
  • Runoff is a vital component of the hydrologic cycle as it represents the movement of water from land to bodies of water. Factors that influence its occurrence include precipitation intensity, soil saturation levels, land use changes such as urbanization, and vegetation cover. When rainfall exceeds the capacity of soil to absorb water, it results in increased runoff which can contribute to river flow and groundwater recharge.
• Discuss the environmental implications of increased runoff due to urbanization and how it affects local ecosystems.
  • Increased runoff due to urbanization leads to higher volumes of water flowing rapidly into rivers and lakes. This can cause flooding, erosion, and sedimentation in aquatic habitats. Moreover, urban runoff often contains pollutants such as heavy metals and nutrients from fertilizers, which can degrade water quality and harm local ecosystems. The alteration of natural hydrology can disrupt the balance in aquatic environments, affecting plant and animal life.
• Evaluate strategies that can be implemented to manage runoff effectively in urban settings while considering ecological health.
  • To manage runoff effectively in urban areas, strategies such as green infrastructure can be implemented. This includes creating green roofs, permeable pavements, and rain gardens that allow for better infiltration of water into the soil. Additionally, establishing retention basins can help capture excess runoff during storms. These methods not only reduce flooding but also enhance groundwater recharge and improve water quality by filtering pollutants. A comprehensive approach requires collaboration among city planners, ecologists, and community stakeholders to promote sustainable practices.

Related terms

Infiltration: The process by which water on the ground surface enters the soil.

Evapotranspiration: The combined processes of evaporation from the land and transpiration from plants, returning water vapor to the atmosphere.

Watershed: An area of land that drains rainwater and snow into a common outlet, such as a river or lake.