Download Chapter 7: Air, Water, and Energy Lesson 6: Earth`s Fresh Water

desalination
Chapter 7: Air, Water, and Energy
Lesson 6: Earth’s Fresh Water
water cycle
groundwater
Objectives:
 Explore how salt water can be used to make fresh water.
 Compare salt water and fresh water resources.
 Recognize how water can become polluted.
 Identify ways to clean up and conserve water.
MAIN IDEA: Fresh water is constantly renewed by the water cycle.
water table
aquifer
spring
well
reservoir
1. How Do We Use Earth’s Oceans?
i. 97% of water is salt water.
ii. 3% is fresh water
1. 69% of fresh water is frozen in glaciers and icebergs
2. Less than 1% of freshwater is on the surface
3. The remaining 30% is below ground, as groundwater.
a. Seafood
b. Minerals – a pail of seawater contains almost every known element.
a. Hot water bubbling out of under water volcanoes is especially
mineral rich
b. Metals such as tin and gold are found on the sea floor.
c. Fossil Fuels – offshore rigs pump oil and natural gas from beneath the
ocean floor.
d. Fresh water – desalination
a. Desalination helps remove dissolved salts and materials from
seawater to make it usable.
b. Desalination plants aid this process.
i. Seawater enters the plant is heated.
ii. The boiling seawater is then pushed into another chamber
iii. As water evaporates, it leaves the dissolved materials
behind.
Why are oceans a valuable resource?
Oceans are a valuable resource because they supply seafood, minerals,
fossil fuels, and water.
2. Where Is Fresh Water From?
a. Fresh water is constantly renewed by the water cycle.
i. Water is on the move – as a liquid that changes to a gas (water
vapor) and back to liquid.
ii. When water evaporates, remember, it leaves behind the
material it contained.
1. The water vapor is not salt water.
iii. When water falls back to Earth some of it seeps into the
ground, as groundwater.
iv. Then the water starts to back up and fill the spaces in the rocks
and soil above – the top of the water-filled spaces is called the
water table.
v. An underground layer of rock or soil that is filled with water is
called an aquifer.
vi. Some water seeps out of the ground in a spring. Springs occur
when the water meets the surface.
vii. Wells are holes dug below the water table. The water seeps
into the hole. In some wells people get the water out of the
hole with pumps.
viii. Most supplies of fresh water for towns and cities come from
reservoirs. Reservoirs are storage areas for freshwater
supplies.
1. They may be human made or natural lakes or ponds.
Why is groundwater an important part of the water cycle?
Groundwater is an important part of the water cycle because it provides us
with much of Earth’s freshwater supply.
3. How Can Fresh Water Be Polluted?
a. Precipitation – as acid rain
b. Runoff water – water that runs over garbage can end up in streams
and lakes, and oceans
c. Groundwater – as water soaks through the soil, it can pick up
chemicals, such as pesticides.
d. Household waste – we pollute water too.
i. Every time we brush our teeth, wash dishes or clothes.
What are four sources of water pollution?
Runoff water that picks up garbage, groundwater that picks up pesticides,
industrial waste, and household waste.
4. How can we Purify Water?
a. The water cycle cleans water naturally
b. When water seeps into the ground, the ground acts as a fine screen,
or filter. Most dirt particles are trapped, or filtered out, as water
seeps into the ground.
c. Freshwater supplies for large areas can be cleaned on a large scale.
What are the three ways that water is purified?
The water cycle, filtration through the ground, and large scale water
purification.