Where is fresh water found? Chapter 7 Lesson 2

Learning Target/Vocabulary  Students will be able to describe the various forms of fresh water.  Vocabulary: aquifer, water table, reservoir

Fresh Water  Less than 3/100 of Earth’s water is fresh water. This is the water we use for drinking, cooking, and cleaning. We also use this water to grow crops, make electricity, and make many products.

Fresh Water  Almost all of Earth’s fresh water starts as rain or snow.  Fresh water is not evenly spread over the world. Some places have much more fresh water than others. But no matter where you are, there is only a limited amount of fresh water.

Fresh Water  Scientists can help communities to use water wisely. They can give communities information about the location of underground water and about the water’s quality.  Scientists can also provide technology that reduces the amount of water a community needs.

Groundwater Rain and melted snow that soaks into the ground is called groundwater. Groundwater occupies an aquifer, which is comprised of layers of rock and soil. The top level of ground water in an aquifer is the water table. Aquifer- The layer of rock and soil that groundwater flows through. (page 203 science book) Water Table- The top level of groundwater in an aquifer.

Aquifer- The layer of rock and soil that groundwater flows through. (page 203 science textbook) book)

Review Questions  What is an aquifer? An aquifer is the layers of rock and soil that groundwater occupies. Where do you think your local community gets its fresh water? Potential Answers: Groundwater, surface water, lakes, or rivers. What is likely to have an impact on your local fresh water supply? Rainfall, snowfall, runoff from farmland, pollution, overuse, or conservation.

Rivers  Surface waters include rivers, streams, and lakes.  Most rivers eventually flow into the ocean.  What is the continental divide?  The area from which water drains into a river is called the river’s watershed.

Rivers Continued  What happens on the land in a watershed can affect places far away. If chemicals are placed in the watershed, they may be carried by water to rivers.  Rain water may erode soil from fields and construction sites. This soil could run into the rivers and cause changes to the ecosystem downstream.  Many researchers are studying how these and other issues affect watersheds.

Reservoir  Reservoir- An artificial lake that forms behind a dam.

Ice  About 7/10 of Earth’s fresh water is frozen into ice and makes up glaciers and ice sheets.  Much of Earth’s ice is on Greenland and Antarctica.  In these places, huge ice sheets cover most of the land. The ice sheets are several kilometers thick in some places.  Glaciers and ice sheets flow, they crush and move rock, changing the shape of the land.  In places where glaciers and ice sheets reach the ocean, large pieces of ice can break off forming icebergs.

Review Questions Where is most of Earth’s ice found? Greenland and Antarctica Use a map of the United States to predict what would happen to a chemical dumped into the Mississippi River near St. Paul Minnesota. It would likely travel downriver and eventually end up in the Gulf of Mexico Approximately how much of the fresh water we in the United States use comes from the ice sheets covering Greenland? Very little because melting ice probably runs off to the ocean and areas with large populations in the United States are far away.

Getting Water to Homes  People may use groundwater or surface water as a source of fresh water.  Water is usually treated to clean it of harmful materials before it is used.  (Page has a great diagram in the science book of the workings of a water treatment plant.

Water Treatment  Water is treated to kill bacteria and remove pollutants.  Pollutants could potentially get into groundwater through chemical runoff from farm fields, parking lots, or lawns and sink into the ground.  Do you think that bottled or tap water has fewer pollutants? Consideration should be given to a purification process, bacteria in water at the source, bacteria in the supply system, bacteria in the bottles, sterilization, chemicals added, and quality control.

Average Daily Water Use (Per Person) Toilet Flush71 Liters Laundry57 Liters Shower/bath49 Liters Other38 Liters

What is the water cycle?  Earth’s water does not sit still. It changes form and moves from place to place.

Water in the Air  If you look around the room can you see water around you?  Water surrounds you all the time. This water is not in a liquid form as in rivers or as a solid form as in glaciers.  This water is an invisible gas called water vapor.  This water vapor was liquid water at some time in the past.  It may have been water inside a plant, in a tropical river, or in the Arctic ocean.

Water Vapor  Water vapor makes up a very small fraction of the gases in the air. The particles of water vapor, like particles of other gases, are constantly moving.  Air pressure is the pressure of these gas particles against another object. Air pressure pushes in all directions because the gas particles move in all directions. Air pressure decreases as you move higher in the atmosphere.

The Water Cycle  The Water Cycle- Bill Nye The Water Cycle- Bill Nye  Steps of the water cycle include evaporation, condensation, precipitation, and runoff.  These steps can be affected by temperature, pressure, wind, and the elevation of the land.

Steps of the Cycle and their Meaning  Evaporation- Changing of liquid water to water vapor.  Condensation- The water vapor turns into liquid, such as water droplets in clouds.  Precipitation- The water falls from clouds as rain, snow, sleet, or hail.  The water cycle has many different paths that can be taken.  Condensation for example does not happens only in the making of clouds. Condensation also forms dew.

Sublimation  Sublimation is another possible path in the water cycle.  Sublimation- Is ice changing into water vapor without first melting. Example- When ice cubes in a freezer shrink over a long period of time.  Sublimation happens more slowly than evaporation. Lower temperatures slow the rate of sublimation.

Water Vapor  Water vapor may freeze directly into ice without first becoming liquid water.  The ice crystals that form on surfaces are called frost.

WaterLiquidSolid EvaporationAll None CondensationAll None PrecipitationAllSome SublimationAllNoneAll

Water Cycle  There are many paths of the water cycle.  Water is used by and made in living things.  The energy of sunlight causes most melting, evaporation, and sublimation.  Page Water Cycle- different paths of the water cycle. (Great visual aid!)

Review Questions Where does evaporation take place? Water evaporation from oceans, lakes, and puddles. How does the energy of the Sun affect Earth’s water cycle? As the Sun heats the Earth, the water evaporates due to the warmer temperatures.