Surface runoff

Definition

Surface runoff is the flow of water that occurs when excess rainwater, melted snow, or irrigation water flows over the ground's surface rather than being absorbed into the soil. This phenomenon is a critical part of the hydrological cycle, as it contributes to the movement of water from land to rivers, lakes, and oceans, affecting water quality and quantity in various ecosystems.

5 Must Know Facts For Your Next Test

1. Surface runoff can lead to erosion, transporting soil and pollutants into waterways, which affects water quality.
2. Factors such as soil saturation, land use, vegetation cover, and topography greatly influence the amount of surface runoff in a given area.
3. Urbanization increases surface runoff due to impervious surfaces like roads and buildings that prevent water absorption into the ground.
4. Surface runoff is a significant component of flooding events, particularly during heavy rainfalls when the ground cannot absorb all the water.
5. Best management practices for surface runoff include creating retention basins, green roofs, and permeable pavement to reduce excess flow.

Review Questions

• How does surface runoff impact water quality in nearby bodies of water?
  • Surface runoff significantly impacts water quality by carrying pollutants such as sediments, fertilizers, and pesticides into rivers and lakes. When rainwater flows over agricultural or urban areas, it picks up these contaminants and transports them directly into local waterways. This can lead to eutrophication, harmful algal blooms, and other issues that harm aquatic ecosystems and affect drinking water supplies.
• Discuss how urbanization affects surface runoff patterns and what measures can be taken to mitigate its effects.
  • Urbanization alters natural drainage patterns by replacing permeable surfaces with impervious materials like asphalt and concrete. This increases surface runoff because water cannot infiltrate the ground, leading to more frequent flooding and reduced groundwater recharge. To mitigate these effects, cities can implement measures such as green infrastructure, including rain gardens and permeable pavements, which enhance infiltration and reduce runoff volumes.
• Evaluate the role of surface runoff in the hydrological cycle and its implications for watershed management.
  • Surface runoff plays a crucial role in the hydrological cycle by transferring excess water from land to bodies of water. It affects watershed management by influencing water availability, sediment transport, and pollutant distribution within an ecosystem. Effective watershed management must consider surface runoff patterns to develop strategies that balance water conservation with flood control while protecting water quality. This requires integrated approaches that account for land use planning and environmental protection measures.

Related terms

infiltration:

The process by which water on the ground surface enters the soil, becoming part of the groundwater system.

watershed: An area of land that drains rainwater or snowmelt into a single body of water, such as a river, lake, or ocean.

stormwater management:

A set of practices designed to manage the quantity and quality of stormwater runoff to minimize flooding and pollution.