transpiration The release of water vapor into the air through the leaves of plants; some-
times called evapotranspiration.
water cycle The cycle through which water moves around the Earth, changing both its
phase (between solid to liquid to gas) and its location (in the oceans, in clouds, in
streams and lakes, and in groundwater).
water vapor Water in the form of a gas. Water vapor is invisible to humans; when we see
clouds, we actually are seeing liquid water in the clouds.
Points to Consider
- How does precipitation affect the topography of the Earth?
- What natural disasters are caused by the water cycle?
- How might pollution affect creatures far from the source of the pollution?
- How might building dams disrupt the natural water cycle?
- If the temperature of the Earth increases through global warming, how might the water
cycle be altered?
13.2 Surface Water.
Lesson Objectives
- Compare streams and rivers and their importance.
- Describe what ponds and lakes are, and why they are important.
- Explain why wetlands are significant in the water cycle, and describe their biodiversity.
- Describe the causes of floods and their effects.
Introduction
As we’ve learned, some of the freshwater on the Earth is on the surface, in streams, rivers,
ponds and lakes. This freshwater is tremendously important to humans, plants, and animals.
Wetlands are areas where water bodies and land meet. Wetlands contain high biodiversity
and play a key role in naturally removing pollutants from water. At times, surface waters
flood, which often creates hazardous conditions for people on the ground.
Streams and Rivers
Astream is a body of moving water confined by a bottom (or bed) and earthen sides
(or banks). There are many categories of streams including creeks, brooks, tributaries,