Runoff

Runoff is the movement of water over the Earth's surface. When rain falls, it can either soak into the ground or flow across the surface. Runoff occurs when the ground is unable to absorb all the water, which can happen if the soil is already saturated, or if the rain is falling too quickly for the soil to absorb it all.

Runoff can occur in urban and rural areas, and it can have both positive and negative impacts. In urban areas, runoff can cause flooding and erosion, and can pick up pollutants from roads and buildings, which can then be carried into rivers and lakes. In rural areas, runoff can contribute to soil erosion, and can also carry fertilizers and pesticides from agricultural fields into waterways, which can harm aquatic ecosystems.

Study Guide

1. What is runoff?
   Runoff is the movement of water over the Earth's surface.
2. When does runoff occur?
   Runoff occurs when the ground is unable to absorb all the water, which can happen if the soil is already saturated, or if the rain is falling too quickly for the soil to absorb it all.
3. What are the impacts of runoff in urban areas?
   In urban areas, runoff can cause flooding and erosion, and can pick up pollutants from roads and buildings, which can then be carried into rivers and lakes.
4. What are the impacts of runoff in rural areas?
   In rural areas, runoff can contribute to soil erosion, and can also carry fertilizers and pesticides from agricultural fields into waterways, which can harm aquatic ecosystems.