March+8

=**Thinking More About Investigation 2**= Earth’s Groundwater Supply


 * Bell Ringer**: What is groundwater?

Since you learned about the problem in Fruitvale you have decided that you need to know more about groundwater. To help you learn more, read the following information about the earth’s groundwater supply.
 * INDIVIDUAL READING**

Try to imagine all of Earth’s water sources. How many come to mind? There are oceans, seas, lakes, reservoirs, ponds, polar ice caps, glaciers, icebergs, snow fields, rivers, streams, creeks, and groundwater.

If the contents of a 2-liter bottle represented all the water on Earth, what fraction of the bottle do you think would represent the salt water found in the oceans and seas? How much of the water in the bottle would represent the supply of fresh water found at the surface of the earth? How much would represent the groundwater, the under- ground supply of fresh water?

Believe it or not, 1,948 mL out of the total 2,000 mL, or about 97.5%, would be salt water! All the earth’s fresh water would be only 52 mL— barely enough to make a popsicle. If you took away all of the ground- water, including all the water frozen into ice caps and glaciers, you would be left with 0.28 mL of water—less than 5 drops—to represent every bit of the fresh water found on the Earth’s surface in all of its lakes and rivers.

The amount of fresh water on the surface of the Earth depends on your location, landscape, and climate. About 50% of the fresh water used in homes throughout the U.S. comes from surface water sources. The other 50% of the homes in the U.S. obtain their water from underground aquifers, which are layers of rock through which water can flow and be stored. Some of these people get the water from their own private wells, while others obtain it from wells operated by municipal (city or town) water departments. Although they are dif- ferent, groundwater and surface water supplies are related and inter- connected. Surface water is continually soaking into the ground and becoming groundwater. At the same time, groundwater is continually being removed by humans or by natural processes such as seeps and springs, which keep water flowing into lakes, streams, and rivers even when there is a drought.

The amount of water in the ground depends on climate, the amount of water seeping into the ground, and the type of soil and rock. The depth below the Earth’s surface at which groundwater can be found often changes. This depth defines the upper boundary of saturated ground and is called the water table. The water table rises closer to the surface during times of wet weather and sinks farther from the surface during times of drought or heavy pumping from water wells. A well that has dried up often indicates a lowered water table.

Although groundwater is an excellent source of drinking water, by its very nature it is never “pure” water. As water from various sources, such as precipitation (rain, snow, etc.) and agricultural irrigation, soaks into and through the earth’s layers, it collects and carries dis- solved and suspended materials with it. Although soil does act as a natural filter and often helps remove some dangerous substances from water, it can also be a source of natural contaminants such as radioac- tive minerals (radium) and gases (radon), toxic substances given off by organisms, and disease-causing microbes such as giardia and amoebas. The human population adds to this natural contamination through the use of pesticides, fertilizers, and other chemicals that can soak into the earth. Humans also add to contamination by accidental chemical spills and undetected leaks in storage tanks, sewage pipes, and landfills. Chemical pollutants released into the air can be trans- ported back to the earth, and into the groundwater, by rain and snow.

**Group (ANSWER ON THE RESPONSE SHEET IN YOUR FOLDER)**
1. What is groundwater? Why is it important? 2. Where does the water that you drink come from? 3. What concerns do you have about the water supply in your region? 4. What concerns do you have about the quality of the water in your region? 5. Did you learn any new information or read anything that will affect how you think or act?

**Individual (ANSWER IN [|MOODLE- JOURNAL -GROUNDWATER])**
1. How can surface water become contaminated? How can ground- water become contaminated? 2. Describe some advantages and disadvantages associated with using water from an aquifer.

Hangman Game: http://www.quia.com/hm/504653.html