Water is found everywhere on the Earth and in the atmosphere in the form of ice, liquid and vapor. Some interesting water facts:

• 97.24% of the Earth's water is found in the salty oceans.
• 2.14% is found in icecaps and glaciers.
• 0.02% of water is found in inland seas and lakes.
• 0.61% of the Earth's water is found underground in aquifers and soils.

Of all the water on Earth, 99.7% of that water is unusable by humans. Only 0.3% of Earth's water is utilized by humans for drinking, washing, cooking and other daily routines (http://wwwga.usgs.gov/edu/earthwherewater.html).

Drinking water is generally clean in the U.S. because of strict drinking water quality standards. Although drinking water standards regulate the water that comes from our tap, these standards may actually vary due to the water source and treatment methods. It is important to regulate drinking water because many contaminants occur naturally in waterways. There is no such thing as completely "pure water."

Drinking water comes from many different sources. One large source is surface water, such as lakes, rivers or reservoirs. If there is no surface water source near your community, then the water may comes from an underground water source such as an aquifer. Wells often tap into the natural aquifers that exist below the surface ground and run all over the Earth. Aquifers can be very small or many miles long. It is important to consider how your source of drinking water is affected by acts of nature and humans. It is not just what happens in the lake, reservoir or well, but what happens over the whole watershed as was discussed in Lesson 3, An Underground River.

Drinking water directly from a well or surface source can be dangerous, as that source may already be full of contaminants. There are compounds present in water that may be harmful to the organisms that use that water source. The compounds can be naturally occurring — such as metals or minerals from rock erosion, or human-induced — such as fertilizer run-off, factory discharges or dissolved pharmaceuticals. Water dissolves or absorbs whatever it comes in contact with, and this can be dangerous if the substances are harmful.

Contamination in the water can negatively affect the organisms that come in contact with it. The affects can be acute or cause illness and death. Microbial organisms and large chemical spills in drinking water can cause acute affects. Contaminants can also cause chronic effects in humans, which occur over time after drinking water with dangerous levels of contaminants. Some examples of chronic effects are: cancer, liver and kidney problems. These are most often due to chemical spills, high levels of minerals and other toxins.

Environmental engineers are concerned about making drinking water safe for citizens. These engineers determine what contaminants are in the water that may harm people, other species or the environment. Environmental engineers determine levels of contaminants, sources of contaminants and the effects of contaminants. These engineers monitor industrial and commercial inputs to watersheds as well as natural changes in the watershed from temperatures and time. If industrial inputs are present, engineers track the sources upstream and hold the company responsible for what they are dumping. Engineers use this information to create municipal water treatment plants that remove harmful contaminants from the water. They also take into consideration the water taste. Engineers must be able to design and create a safe water product that tastes and smells acceptable so people will use it. All of these factors are considered when designing a drinking water treatment or remediation system.

A water table is the surface that divides the vadose zone and the saturated zone of the earth's crust. The vadose zone is the zone that is exposed to the atmosphere with pore spaces between the individual grains of soil filled mostly with air. The saturated zone is the zone below the water table where the pore spaces of the soil are filled mostly with water. The water table moves up and down with variations in weather, temperature, and precipitation. Because the topography of the earth's surface is variable, the water table can produce features such as rivers, wetlands, and lakes in low valleys. These water features then change directly with the changing level of the water table.

Figure 3. The water table is the interface between the saturated zone and the vadose zone. click for copyright

Groundwater is the water source that comes from aquifers below the Earth's surface. These are underground water-bearing sections of permeable rock, sand or gravel. (For more on aquifers, please visit the U.S. Geological Survey's Water Science for Schools website at: http://ga.water.usgs.gov/edu/earthgwaquifer.html). About 20% of water used by humans comes from groundwater. Mostly, groundwater sources are used in areas that have few fresh lakes and streams.

The amount of groundwater being used in the U.S. for personal and commercial uses has increased since the 1950s. For the 43 million Americans who supply their own water at home, 99% of them use groundwater well sources. The groundwater supply is tapped into by digging or drilling water wells.

Environmental engineers spend much time studying groundwater. They make models of groundwater flow to determine which communities can use different aquifers for their water supply. They demonstrate how groundwater moves so they can determine how contaminants spread underground from industrial spills and landfill leaching. They analyze the physical properties of the groundwater to determine how safe it is and how it can be used. Engineers dig wells and tap into this water resource. Water levels in the well do not always remain constant, but change due to seasonal temperatures and precipitation. Engineers design pumps — that accommodate changes in water levels — to move water out of the well at a constant rate, yet not completely deplete the source; otherwise, if the water level falls below the pump, the well will only pump air, and the well will go dry. Only 20% of our water supply comes from groundwater; however, more groundwater exists on the Earth than the amount of water in lakes and streams. It is important for engineers to be able to utilize groundwater sources in places of increasing temperatures due to global warming and decreasing surface fresh water supplies. Here is a site on digging water wells and well types: http://ga.water.usgs.gov/edu/earthgwwells.html.

It is important for citizens to understand just how easily — even if it's mistakenly — they can contribute to the contaminants in drinking water and what treatment can be done to counteract these harmful effects. Citizens can learn how to help engineers protect our natural water sources.

Know/Want to Know/Learn (KWL) Chart: Before the lesson, ask students to write down in the top left corner of a piece of paper (or as a group on the board) under the title, Know, all the things they know about groundwater. Next, in the top right corner under the title, Want to Know, ask students to write down anything they want to know about groundwater. After the lesson, ask students to list in the bottom half of the page under the title, Learned, all of the things that they have learned about groundwater. Ask students to name a few items and write them on the board.

Question/Answer: Ask students the following questions to review their previous knowledge of groundwater flow:

1. What is an aquifer? (Answer: An aquifer is water under the ground that technically provides a useable amount of water when pumped.)
2. Why do engineers and many people care about groundwater? (Answer: because many people get their drinking water from the groundwater)
3. If a can of oil was spilled on the ground by the school, could it end up in the town well 5 miles south of the school? (Answer: Yes, the oil will infiltrate through the ground and then travel with the groundwater in the direction of groundwater flow. The oil will not end up in the town well, however if the groundwater dose not flow south.)

Brainstorming: Have students work in pairs to brainstorm a list of ways groundwater could become polluted. Each pair should write five ways down on a piece of paper. Then, as a class get one answer from each ground and record it on the board. (Some examples include: not probable disposing of oil after an oil change, an industry dumping chemicals, using pesticides on a farm or lawn, etc.)

Engineering Design: Have students work in groups of 3 or 4 to design a system to stop a known polluted aquifer from migrating further and reaching a town well. Students should create a poster of their design and present the poster to the class. This is a creative activity and does not stress the technical viability of the treatment. If students are having trouble thinking of ideas, they can research on the Internet. Have students use a search engine (i.e., google.com or yahoo.com) to search for groundwater treatment for ideas. (Some ideas include: try to pump all the pollution out, build a wall to stop the pollution from migrating, add something to the water that will treat the pollutant or rely on bioremediation.)

Is it clean?: After the students have completed the two drinking water activities, ask them to brainstorm with a partner on what other tests might need to be performed on water to determine if it is clean and safe to drink. Have the student pairs make lists of possible water quality tests, including ones they have used in this unit thus far. Ask students to create a preliminary flow chart of how to collect and treat drinking water from a groundwater aquifer all the way to the faucet in their house.