Fresh Water
Earth is called the “water planet” because nearly ¾ of Earth is made up of water. 97% salt water 3% fresh water Less than 1% of the water on Earth is usable to humans. CFU (check for understanding): How much of the water on Earth is usable?
Water is found in several forms on Earth, including: Oceans Ice (glaciers) Rivers and lakes Groundwater Far more fresh water is found underground than in all of Earth's rivers and lakes. CFU: Is there more freshwater above ground or below ground?
In addition to household purposes, people use water for agriculture, industry, transportation and recreation.
Water is also important for living things to grow, reproduce, and carry out other important processes. Example: Plants need water to carry out photosynthesis.
A river and all its tributaries together make up a river system. tributaries=the smaller streams and rivers that feed into a main river due to the pull of gravity. CFU: What is a river system?
All the water in a river system drains into the main river All the water in a river system drains into the main river. The land area that supplies water to a river system is called a watershed (also called drainage basins). CFU: What is a watershed?
One watershed is separated from another by a ridge of land called a divide. Streams on each side of the divide flow in different directions. The Continental Divide is the longest divide in North America. CFU: What is a divide?
A flood occurs when the volume of water in a river increases so much that the river overflows its channel. Flood water has a lot of energy and can uproot trees and wash away bridges and houses.
Ponds and lakes form when water collects in hollows and low-lying areas of land. They are made up of still, or standing water. Ponds are generally smaller and shallower than lakes. CFU: What is the difference between ponds and lakes?
Ponds have many plant species living in them because of how shallow they are, which allows sunlight to reach all the way to the bottom. The bottom of a pond is usually covered with mud and algae. Not all ponds exist-year round. Some dry up in the summer and reappear when runoff from spring rains and melting snow collects in low areas. CFU: Why do ponds have a lot of plant species in them?
Most lakes are deep enough that sun does not reach all the way to the bottom. A lake bottom may usually consist of sand, pebbles or rock. CFU: Why is a lake’s bottom usually rocks and pebbles?
People can create a lake by building a dam across a river People can create a lake by building a dam across a river. The lake may be used for supplying drinking water, irrigating fields or for boating and fishing. A reservoir is a lake that stores water for human use. CFU: What is a reservoir?
A lake environment can gradually change over time.
When a glacier reaches the seacoast, icebergs form When a glacier reaches the seacoast, icebergs form. About 90% of an iceberg lies below the surface. The underwater part is a hazard to ships because it is often much wider than the visible part. CFU: How much of an iceberg is above the surface?
Groundwater comes from precipitation that soaks into the ground instead of evaporating. Water underground trickles down between particles of soil and through cracks and spaces in layers of rock. People can bring groundwater to the surface through the use of a well. CFU: How do people usually get water from underground?
A wetland is an area of land that is covered with a shallow layer of water during some or all of the year. They form in places where water is trapped in low areas or where groundwater seeps onto the surface of the land. Examples: marshes, swamps and bogs CFU: What is a wetland?
Because of their sheltered waters and rich supply of nutrients, wetlands provide habitats for many living things. Wetlands also naturally filter water and help control floods by absorbing extra runoff from heavy rains. CFU: Give two reasons why wetlands are beneficial to us?
The Florida Everglades and other wetlands are protected by laws to protect many endangered species that live there.