Water
Quality
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Water Quality
Water quality is a term used to describe the chemical, physical, and biological characteristics of water, usually in respect to its
suitability for a particular purpose. Although scientific measurements are used to define a water's quality, it's not a simple thing to
say that "this water is good," or "this water is bad." After all, water that is perfectly good to wash a car with may not be good
enough to serve as drinking water at a dinner party for the President! When the average person asks about water quality, they
probably want to know if the water is good enough to use at home, to play in, to serve in a restaurant, etc., or if the quality of our
natural waters are suitable for aquatic plants and animals.
As the diagram below shows, assessment of the occurrence of chemicals that can harm water quality, such as nutrients and pesticides in water resources, requires recognition of complicated interconnections among surface water and ground water, atmospheric contributions, natural landscape features, human activities, and aquatic health. The vulnerability of surface water and
ground water to degradation depends on a combination of natural landscape features, such as geology, topography, and soils; climate and atmospheric contributions; and human activities related to different land uses and land-management practices.
More and more nowadays we are hearing about situations where the quality of our water is not good enough for normal uses. Bacteria and microorganisms have gotten into drinking-water supplies, sometimes causing severe illness in a town; chemical pollutants have been detected in streams, endangering plant and animal life; sewage spills have occurred, forcing people to boil their
drinking water; pesticides and other chemicals have seeped into the ground and have harmed the water in aquifers; and, runoff
containing pollutants from roads and parking lots have affected the water quality of urban streams.
Yes, water quality has become a very big issue today, partly because of the tremendous growth of the Nation's population and urban expansion and development. Rural areas can also contribute to water-quality problems. Medium- to large-scale agricultural
operations can generate in animal feed, purchased fertilizer, and manure, more nitrogen and phosphorus than can be used by crops
or animals. These excess nutrients have the potential to degrade water quality if incorporated into runoff from farms into streams
and lakes All this growth puts great stress on the natural water resources, and, if we are not diligent, the quality of our waters will
suffer.
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Water Quality
The Water Cycle
Earth's water is always in movement, and the natural water cycle, also known as the hydrologic cycle, describes the continuous movement of
water on, above, and below the surface of the Earth. Water is always changing states between liquid, vapor, and ice, with these processes happening in the blink of an eye and over millions of years.
What is the water cycle?
What is the water cycle? I can easily answer that—it is "me" all over! The water cycle describes the existence and movement of water on, in,
and above the Earth. Earth's water is always in movement and is always changing states, from liquid to vapor to ice and back again. The water
cycle has been working for billions of years and all life on Earth depends on it continuing to work; the Earth would be a pretty stale place to
live without it.
A quick summary of the water cycle
Where does all the Earth’s water come from? Primordial Earth was an incandescent globe made of magma, but all magmas contain water. Water set free by magma began to cool down the Earth’s atmosphere, until it could stay on the surface as a liquid. Volcanic activity kept and still
keeps introducing water in the atmosphere, thus increasing the surface- and ground-water volume of the Earth.
The water cycle has no starting point. But, we'll begin in the oceans, since that is where most of Earth's water exists. The sun, which drives the
water cycle, heats water in the oceans. Some of it evaporates as vapor into the air. Ice and snow can sublimate directly into water vapor. Rising
air currents take the vapor up into the atmosphere, along with water from evapotranspiration, which is water transpired from plants and evaporated from the soil. The vapor rises into the air where cooler temperatures cause it to condense into clouds. Air currents move clouds around
the globe, cloud particles collide, grow, and fall out of the sky as precipitation. Some precipitation falls as snow and can accumulate as ice caps
and glaciers, which can store frozen water for thousands of years. Snowpacks in warmer climates often thaw and melt when spring arrives, and
the melted water flows overland as snowmelt.
Most precipitation falls back into the oceans or onto land, where, due to gravity, the precipitation flows over the ground as surface runoff. A
portion of runoff enters rivers in valleys in the landscape, with streamflow moving water towards the oceans. Runoff, and ground-water seepage, accumulate and are stored as freshwater in lakes. Not all runoff flows into rivers, though. Much of it soaks into the ground as infiltration.
Some water infiltrates deep into the ground and replenishes aquifers (saturated subsurface rock), which store huge amounts of freshwater for
long periods of time. Some infiltration stays close to the land surface and can seep back into surface-water bodies (and the ocean) as groundwater discharge, and some ground water finds openings in the land surface and emerges as freshwater springs. Over time, though, all of this
water keeps 3moving, some to reenter the ocean, where the water cycle "ends" ... oops - I mean, where it "begins."
Water Quality Activity
The Water Cycle for Kids: A Placemat
The water cycle is vitally important for every person in the world—from a great grandmother in Nepal to a newborn crying in his crib in
Omaha, Nebraska. The water cycle is a basic scientific concept that is taught even in elementary schools and is one of the first environmental
concepts that children learn. Although the great grandmother might understand our main water-cycle diagram, it might be a bit too complex for
young children.
So, if you're trying to find a simpler diagram of the water cycle meant for young children, we have just what you are looking for. Your child
can learn about the water cycle as you are wiping up spilled orange juice (which is, of course, mostly water) from this place mat. After all,
juice running over the place mat can be considered runoff; if it spills on the floor, that would be freshwater storage (lake); and, if you are outside, the juice soaking into the ground is like infiltration. And, if the juice gets all over their clothes? Now, that is just a big mess, but it does
provide an excellent example of capillary action!
Visit the following link to get you copy of the Water Cycle for Kids http://ga.water.usgs.gov/edu/watercycle-kids.html or better yet give the
students a piece of paper and some art supplies and let them draw their own.
© The Straight Edge, Inc. (http://www.straightedgeinc.com/)
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Water Quality Activity
Write in the letter in the boxes next to the water-cycle terms
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Condensation
Evaporation
Evapotranspiration
Freshwater storage
Groundwater discharge
Groundwater storage
Infiltration
Precipitation
Snowmelt runoff to streams
Spring
Streamflow
Sublimation
Surface runoff
Water storage in the atmosphere
Water storage in ice and snow
Water storage in oceans
Desublimation
Plant uptake
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Water Quality Answers
Activity for students— Have your students choose a water-cycle topic from the list below and have
students research, report and discuss as a group what they have discovered.
Answers for the for the water cycle activity previous page.
A - Storage in ice and snow
B - Precipitation
C - Snowmelt runoff to streams
D - Infiltration
E - Groundwater discharge
F - Groundwater storage
G - Water storage in oceans
H - Evaporation
I - Condensation
J - Water storage in the atmosphere
K - Evapotranspiration
L - Surface runoff
M - Streamflow
N - Springs
O - Freshwater storage
P - Sublimation
Credits:
U.S. Geological Survey
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Water Quality
Global water distribution
For an estimated explanation of where Earth's water exists, look at the chart below. By now, you know that the water cycle describes the movement of Earth's water, so realize that the chart and table below represent the presence of Earth's water at a single point in time. If you check
back in a thousand or million years, no doubt these numbers will be different!
Notice how of the world's total water supply of about 332.5 million cubic miles of water, over 96 percent is saline. And, of the total freshwater,
over 68 percent is locked up in ice and glaciers. Another 30 percent of freshwater is in the ground. Fresh surface-water sources, such as rivers
and lakes, only constitute about 22,300 cubic miles (93,100 cubic kilometers), which is about 1/150th of one percent of total water. Yet, rivers
and lakes are the sources of most of the water people use everyday.
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Water Quality
Where is Earth's water?
For a detailed explanation of where Earth's water is, look at the data table below. Notice how of the world's total water supply of about 333
million cubic miles (1,386 million cubic kilometers) of water, over 96 percent is saline. And, of the total freshwater, over 68 percent is locked
up in ice and glaciers. Another 30 percent of freshwater is in the ground. Thus, rivers and lakes that supply surface water for human uses only
constitute about 22,300 cubic miles (93,100 cubic kilometers), which is about 0.007 percent of total water, yet rivers are the source of most of
the water people use.
Water source
Water volume, in
cubic miles
Percent of
freshwater
Percent of
total water
321,000,000
—
96.5
Ice caps, Glaciers, & Permanent Snow
5,773,000
68.6
1.74
Groundwater
5,614,000
—
1.7
Fresh
2,526,000
30.1
0.76
Saline (Salt)
3,088,000
—
0.93
Soil Moisture
3,959
0.05
0.001
Ground Ice & Permafrost
71,970
0.86
0.022
Lakes
42,320
—
0.013
Fresh
21,830
0.26
0.007
Saline (Salt)
20,490
—
0.007
Atmosphere
3,095
0.04
0.001
Swamp Water
2,752
0.03
0.0008
Rivers
509
0.006
0.0002
Biological Water
269
0.003
0.0001
Oceans, Seas, & Bays
Source: Igor Shiklomanov's chapter "World fresh water resources" in Peter H. Gleick (editor) 1993, Water in Crisis: A
Guide to the World's Fresh Water Resources (Oxford University Press, New York)
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Links for additional information—URL: http://ga.water.usgs.gov/edu/watercycle.html
Water Quality
The atmosphere is full of water
The water cycle is all about storing water and moving water on, in, and above the Earth. Although the atmosphere may not be a great storehouse of water, it is the superhighway used to move water around the globe. Evaporation and transpiration change liquid water into vapor,
which ascends into the atmosphere due to rising air currents. Cooler temperatures aloft allow the vapor to condense into clouds and strong
winds move the clouds around the world until the water falls as precipitation to replenish the earthbound parts of the water cycle. About 90
percent of water in the atmosphere is produced by evaporation from water bodies, while the other 10 percent comes from transpiration from
plants.
There is always water in the atmosphere. Clouds are, of course, the most visible manifestation of atmospheric water, but even clear air contains
water—water in particles that are too small to be seen. One estimate of the volume of water in the atmosphere at any one time is about 3,100
cubic miles (mi3) or 12,900 cubic kilometers (km3). That may sound like a lot, but it is only about 0.001 percent of the total Earth's water volume of about 332,500,000 mi3 (1,385,000,000 km3), as shown in the table below. If all of the water in the atmosphere rained down at once, it
would only cover the ground to a depth of 2.5 centimeters, about 1 inch.
How much does a cloud weigh?
Do you think clouds have any weight? How can they, if they are floating in the air like a balloon filled with helium? If you tie a helium balloon to a kitchen scale it won't register any weight, so why should a cloud? To answer this question, let me ask if
you think air has any weight—that is really the important question. If you know what air pressure and a barometer are, then you know that air
does have weight. At sea level, the weight (pressure) of air is about 14 ½ pounds per square inch (1 kilogram per square centimeter).
Since air has weight it must also have density, which is the weight for a chosen volume, such as a cubic inch or cubic meter. If clouds are made
up of particles, then they must have weight and density. The key to why clouds float is that the density of the same volume of cloud material is
less than the density of the same amount of dry air. Just as oil floats on water because it is less dense, clouds float on air because the moist air
in clouds is less dense than dry air.
We still need to answer the question of how much a cloud weighs. For an example, let's use your basic "everyday" cloud—the cumulus cloud
with a volume of about 1 cubic kilometer (km) located about 2 km above the ground. In other words, it is a cube about 1 km on each side. The
National Oceanic and Atmospheric Administration (NOAA) provides some estimates of air and cloud density and weight. NOAA found that
dry air has a density of about 1.007 kilograms/cubic meter (kg/m3) and the density of the actual cloud droplets is about 1.003 kg/m3. In the final
calculations, the 1 km3 cumulus cloud weighs a whopping 2.211 billion pounds (1.003 billion kilograms)! However, remember that air also has
mass, so the cloud floats because the weight of the same volume of dry air is even more, about 2.220 billion pounds (1.007 billion kilograms).
So, it is the lesser density of the cloud that allows it to float on the dryer and more-dense air.
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Water Quality Activity
1. How much water do you use when you take a shower? Wash a load of clothes? Flush a toilet? Even brush your teeth? One important measurement of water use is how much water one
person uses in one day, or per-capita water use (per is Latin for by and capita is Latin for
head). The number is usually expressed as gallons of water used per person per day. Visit one
of the sites below to figure out your water usage.
Materials:
· Internet access
http://wecalc.org/calc/#
http://www.csgnetwork.com/waterusagecalc.html
http://www.tampagov.net/dept_water/information_resources/saving_water/
Water_use_calculator.asp
2. As the population of the United States and the world keeps growing, more pressure is put
on our water resources. In the coming decade, what do you think the most serious problem
will be concerning your water situation? Will it be water shortages, water made undrinkable
by pollution, a breakdown in the infrastructure to obtain and supply water ... or will there not
be any major water problems at all? Have a discussion on this with your students.
We will not have enough water
Water will be too polluted
Drinking water will be unsafe
Water systems (infrastructure) will break down
There won't be major water problems
3. How much water does a leaking faucet waste? Check your faucets at home -- do any of them
drip? Well, maybe it's just a small drip -- how much water can a little drip waste? True, a single drip
won't waste much water. But think about each faucet in your home dripping a little bit all day long.
What if every faucet in every home on your block ... in your town ... in your state also dripped? The
drips would add up to a flood of water wasted down the drain.
There is no scientific definition of the volume of a faucet drip, but after measuring a number of
kitchen and bathroom sink faucets, for our calculations below (numbers are rounded), we are going
to use 1/4 milliliter (ml) as the volume of a faucet drip . So, by these drip estimates:
·
·
One gallon: 15,140 drips
One liter: 4,000 drips
Looking at it this way, it seems like that drop of water down the drain is pretty insignificant.
Visit http://ga.water.usgs.gov/edu/sc4.html and test your homes drips.
4. How much water does it take to grow a hamburger? Water is needed to grow not only everything we eat but also to produce almost all the products we use every day. This water is either supplied by nature as precipitation and/or added by people during the growing/production process. You
can't tell by the size of a product or the appearance of a food how much water was actually used to
produce the item.
Visit http://ga.water.usgs.gov/edu/sc1.html to enter your guess on how much water is used to produce some common foods and products. But, please realize this whole exercise is meant to give you
an estimate of how much water is needed in food and product production. Another consideration is
how far back do you go in the chain of production to estimate water use? For beef, some estimates
only consider water for cattle to drink, while other sources may consider the water needed to grow
the food that the
cow eats.
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Credits:
U.S. Geological Survey
Water Quality Activity
Water Properties True/False Quiz
Water is more than just plain old water -- it actually has some very unusual properties. It would be boring if I just told
you that water is wet and clear. So, instead, here are some "maybe true/maybe false" water properties. See if you know
the real water facts.
1. Water contracts (gets smaller) when it freezes.
True
False
2. Water has a high surface tension.
True
False
3. Condensation is water coming out of the air.
True
False
4. More things can be dissolved in sulfuric acid than in water.
True
False
5. Rainwater is the purest form of water.
True
False
6. It takes more energy to heat water at room temperature to 212o F than it does to change 212o F water to steam.
True
False
7. If you evaporate an 8-inch glass full of water from the Great Salt Lake (with a salinity of about 20% by weight), you
will end up with about 1 inch of salt.
True False
8. Sea water is slightly more basic (the pH value is higher) than most natural fresh water.
True
False
9. Raindrops are tear-shaped.
True
False
10. Water boils at a lower temperature at Denver, Co. than at the beach.
True
False
Credits:
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U.S. Geological Survey
Water Quality Answers
(1) Water contracts (gets smaller) when it freezes. FALSE Actually, water expands (gets less dense) when it freezes, which is unusual for liquids. Think of ice -- it is one of the few items that floats as a solid. If it didn't, then lakes would freeze from the bottom up (that would mean we'd
have to wear wet suits when ice skating!), and some lakes way up north would be permanent blocks of ice.
(2)Water has a high surface tension. TRUE Water has the highest surface tension among common liquids (mercury is higher). Surface tension
is the ability of a substance to stick to itself (cohere). That is why water forms drops, and also why when you look at a glass of water, the water
"rises" where it touches the glass (the "meniscus"). Plants are happy that water has a high surface tension because they use capillary action to
draw water from the ground up through their roots and stems.
(3) Condensation is water coming out of the air. TRUE This is actually true -- water that forms on the outside of a cold glass or on the inside
of a window in winter is liquid water condensing from water vapor in the air. Air contains water vapor (humidity). In cold air, water vapor condenses faster than it evaporates. So, when the warm air touches the outside of your cold glass, the air next to the glass gets chilled, and some of
the water in that air turns from water vapor to tiny liquid water droplets. Clouds in the sky and the "cloud" you see when you exhale on a cold
day are condensed water-vapor particles. It is a myth that clouds form because cold air cannot hold as much water vapor as warm air!)
(4) More things can be dissolved in sulfuric acid than in water. FALSE Not true. Sulfuric acid might be able to dissolve a car, but water isn't
known as the "Universal Solvent" for nothing! It can dissolve more substances than any other liquid. This is lucky for us... what if all the sugar in
your soft drink ended up as a pile at the bottom of the glass? The water you see in rivers, lakes, and the ocean may look clear, but it actually contains many dissolved elements and minerals, and because these elements are dissolved, they can easily move with water over the surface of the
earth.
(5)Rainwater is the purest form of water. FLASE I was surprised at this, but, actually, distilled water is "purer." Rainwater contains small
amounts of dissolved minerals that have been blown into the air by winds. Rainwater contains tiny particles of dust and dissolved gasses, such as
carbon dioxide and sulfur dioxide (yep, acid rain). That doesn't mean rainwater isn't very clean -- normally only about 1/100,000th of the weight
of rain comes from these substances. In a way, the distillation process is responsible for rainwater. Distilled water comes from water vapor condensing in a closed container (such as a glass jar). Rain is produced by water vapor evaporating from the earth and condensing in the sky. Both
the closed jar and the earth (via its atmosphere) are "closed systems," where water is neither added or lost.
(6)It takes more energy to heat water at room temperature to 212o F than it does to change 212o F water to steam. FLASE First, water at
boiling temperature (212o F at sea level) is not really the same as boiling water. When water first reaches boiling it has not begun to turn to steam
yet. More energy is needed to begin turning the boiling liquid water into gaseous water vapor. The bonds holding water molecules as a liquid are
not easily broken. If I remember correctly, it takes about seven times as much energy to turn boiling water into steam as it does to heat water at
room temperature to the boiling point.
(7)If you evaporate an 8-inch glass full of water from the Great Salt Lake (with a salinity of about 20% by weight), you will end up with
about 1 inch of salt. TRUE They don't call it the Great SALT Lake for nothing. Water in the Great Salt Lake varies in salinity both by location
and in time. In this example, we are assuming about a 20-percent salt concentration. In other words, about one-fifth of the weight of the water
comes from salt. And how much saltier is Great Salt Lake water than seawater? Quite a bit. Seawater has a salt concentration of about 3 1/2 percent.
(8) Sea water is slightly more basic (the pH value is higher) than most natural fresh water. TRUE Neutral water (such as distilled water)
has a pH of 7, which is in the middle of being acidic and alkaline. Seawater happens to be slightly alkaline (basic), with a pH of about 8. Most
natural water has a pH of between 6-8, although acid rain can have a pH as low as 4.
(9) Raindrops are tear-shaped. FLASE When you think of a drop of falling water you probably think it looks like . When a drop of water
comes out of a faucet, yes, it does have a tear shape. That is because the back end of the water drop sticks to the water still in the faucet until it
can't hold on any more. But, using high-speed cameras, scientists have found that falling raindrops look more like a small hamburger bun! Gravity and surface tension come into play here. As rain falls, the air below the drop pushes up from the bottom, causing the drop to flatten out somewhat. The strong surface tension of water holds the drop together, resulting in a bun shape (minus the sesame seeds).
(10) Water boils at a lower temperature at Denver, Co. than at the beach. TRUE The boiling point of water gets lower as you go up in altitude. At beach level, water boils at 212o Fahrenheit (100° Celsius). But at 5,000 feet, about where Denver is located, water boils at about 203o F
(95°C), and up at 10,000 feet it boils at 193.7oF (89.9°C). This is because as the altitude gets higher, the air pressure (the weight of all that air
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above you) becomes
less. Boiling occurs when the vapor pressure of water exceeds atmospheric pressure. Since there is less pressure pushing on
a pot of water at a higher altitude, it is easier for the water molecules to break their bonds and attraction to each other and, thus, it boils at a lower
temperature. Yes, it will take longer to cook your noodles on top of Mt. Evans in Colorado than at your beach house.
Ground Water Activity
How much do you know about the water below your feet?
1. The water table is the altitude (below ground) where the water level in a well will rise to when the well taps a confined aquifer.
True False
2. If you ate canned corn last night, there is a good chance that it was irrigated with groundwater.
True False
3. Land subsidence occurs in areas underlain by highly-fractured granite, which is readily dissolved by moving ground
water, especially when the water is slightly acidic.
True False
4. Water can flow in streams even during periods of drought due to groundwater seeping into the streambanks.
True False
5. Artificial recharge to an aquifer can occur when people inject water down into a well to force it back into an aquifer so
they can withdraw it later.
True False
6. Big cities drill deep wells to tap naturally heated water because the heat kills bacteria and the water needs less treatment.
True False
7. Bottled water often is advertised as "artesian well water." Artesian water is ground water that is naturally filtered by an
aquifer composed of fine, porous material—this artesian water can be put directly into bottles.
True False
8. The heaviest users of groundwater for drinking water and other public uses are the Southwest desert States, where surface water is scarce.
True False
9. The porosity and permeability of an aquifer define its ability to yield water to wells in productive amounts.
True False
10. For some wells along the coastline that are drilled into porous aquifers, pumps are turned off twice a day (during periods of high tides), since tides temporarily raise saline ground-water levels, causing saltwater intrusion into freshwater
aquifers.
True False
11. Cities prefer to use groundwater for drinking-water supplies because surface water is in constant contact with streambeds and, thus, contains a higher concentration of dissolved minerals and other substances that must be removed.
True False
12. Excessive pumping of a well can reverse the natural flow of ground water into a river, causing the water level in the
river to fall.
True False
13. Most wells are shallow because a significant amount of water cannot be obtained from wells deeper than about 500
feet. This is because it is difficult for pumps to overcome the force of gravity and push water up to the land surface.
True False
14. The most productive wells tap large open areas in subsurface rocks, including horizontal fissures, caverns, and lava
tubes, which have connections to the land surface, thus allowing the aquifer to be quickly recharged by precipitation.
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True False
15. A cone of depression occurs when you drop your scoop of ice cream (made with groundwater) on the ground on a hot
summer day.
True False
Ground Water Answers
1. FALSE Maybe it is not fair to start off with a trick question, but the correct answer is false. The only thing that makes it false is referring to
"confined aquifer," instead of an "unconfined aquifer." A confined aquifer is an aquifer with layers of generally impermeable rock above and
below the aquifer (aquifers tend to run in horizontal layers below ground). As water flows into this aquifer it gets "squeezed" between the rock
layers, thus causing pressure to build up in the aquifer.
Unconfined aquifers do not have this internal pressure (called artesian pressure), so if you drill a well into it, the water will only rise in the well
casing up to the top of the aquifer (the water table); you will need a pump to get the water to the surface. In a confined aquifer if you drill a well,
the pressure will push water up the well casing; sometimes all the way to the land surface—no pump is needed!
2. TRUE This is true. The American Midwest produces a lot of corn. Nebraska is not known as the "Cornhusker State" for nothing. During
2001, it produced more than 1 billion bushels of corn, third after Iowa and Illinois. Nationwide, Nebraska is the third state in groundwater use
behind California and Texas; Nebraska used 7,710 million gallons per day (Mgal/d) in 2005). Groundwater is used for irrigation more than surface water throughout the Midwest, so it is likely that when you eat canned corn for supper tonight, you are also "drinking" groundwater.
3.FLASE This is false. You might be confusing land subsidence with sinkholes, and this statement is more true for sinkholes (not for the
"granite" part). Sinkholes can occur when water, sometimes a bit acidic in nature, dissolves underground rock, often limestone or dolomite. The
land surface can collapse, often dramatically, into the void space underneath.
Land subsidence takes place on a larger scale and usually is a much slower process, but it still involves land that collapses. Actually, "sinks" is a
more proper term. Land subsidence is a gradual settling or sudden sinking of the Earth’s surface owing to subsurface movement of earth materials. The basic cause of land subsidence is a loss of support below ground. In other words, sometimes when water is taken out of the soil, the soil
collapses, compacts, and drops. This depends on the type of soil and also on the type of rock below the surface.
4. TRUE Lucky for us this is true, because if rivers dried up every time there was drought, we (and the fish) would be in trouble. Although we
only see surface water on the Earth's surface, there is a strong connection between nature's surface-water and groundwater systems.
Groundwater contributes to streams in most geographic areas and climatic settings. The proportion of stream water that comes from from groundwater inflow varies according to a region's geography, geology, and climate. Water scientists (hydrologists) can determine the amount of water
that groundwater contributes to streams by analyzing streamflow hydrographs. This groundwater component of a stream's flow is called "base
flow."
In a USGS study, streams in the United States were studied to see how much of the streamflow came from groundwater flow. The Forest River
Basin in North Dakota is underlain by poorly permeable (water moves through it relatively slowly) silt and clay deposits, and only about 14 percent of its average-annual flow comes from groundwater. In contrast, the Sturgeon River Basin in Michigan is underlain by highly permeable
(water moves through it relatively quickly) sand and gravel, and about 90 percent of its average-annual flow comes from groundwater. The median value for 54 streams was 55 percent from groundwater.
5. TRUE; this is one way of using the same groundwater again and again. Sure, it costs money and takes time to do this, but if the groundwater
is valuable enough (probably because enough surface water is scarce) it may makes sense to artificially inject groundwater back into the same
aquifers it came from for use on another day.
In places where the water table is close to the land surface and where water can move through the aquifer at a high rate, aquifers can be replenished artificially. For example, large volumes of groundwater used for air conditioning are returned to aquifers through recharge wells on Long
Island, New York. In Orlando, Florida, water is spread across small basins, sinks into the ground, and recharges the shallow surficial aquifer to
be used for irrigation of local citrus crop fields.
6. FALSE This is false, even if temperatures do rise the further down you go from the land surface. You do not have to get to the center of the
Earth before things get too hot for comfort. In some deep mines, about 3,000 feet down, temperatures can be as hot as in a desert. Water coming
from these depths is hot, too—but not near the boiling point. Boiling water would be found at much deeper depths.
Besides, it is a lot cheaper to just add some chlorine to water to kill bacteria rather than bear the cost of drilling a well a mile deep. Most aquifers
are much closer to the land surface; many are just meters below the ground.
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Ground Water Answers
7.FALSE This is false. While it is true that artesian water, or even just "plain" well water can sometimes be used directly for bottled water, this
statement is false, because artesian water is not defined as being naturally filtered. A simple definition of artesian water is that it is water in the
ground that is under pressure.
Groundwater occuring in aquifers between layers of poorly permeable rock, such as clay or shale, may be confined under pressure. If such a confined aquifer is tapped by a well, water will rise above the top of the aquifer and may even flow from the well onto the land surface, as in a
spring. Water confined in this way is said to be under artesian pressure, and the aquifer is called an artesian aquifer. The word artesian comes
from the town of Artois in France, the old Roman city of Artesium, where the best-known flowing artesian wells were drilled in the Middle Ages.
8. FALSE This is false, as the states in the Southwest desert use more surface water than groundwater. During 2005, Arizona, Colorado, Nevada,
New Mexico, and Utah used about 9,090 million gallons per day (Mgal/d) of groundwater as compared to about 24,200 Mgal/d of surface water.
It is true that these States are not highly populated, so maybe there is less demand by people for water, and maybe their surface water is enough
to serve their purposes. It is no secret, however, where almost all of the water withdrawals in those States went—irrigation purposes; thus, about
6,910 Mgal/d, or about 76 percent, of groundwater was used for irrigation.
9. TRUE This is true. The two main characteristics of rocks that affect the presence and movement of groundwater are porosity (size and
amount of void spaces) and permeability (the relative ease with which water can move through spaces in the rock). You probably know what a
porous material is—it has lots of void spaces and openings, like a sponge. The rocks under our feet are not totally solid, they are full of cracks,
fractures, and void spaces. For water to exist underground, there must be void spaces to hold it.
However, the rock also must be permeable enough to allow water to move (due mainly to gravity). Rock that is highly permeable has connections
between the fractures and openings. These pathways acts as the highways along which water travels underground, and in the case of the owner of
a well, hopefully towards his/her well.
10.FALSE This one is false, but some of the concepts are true. The water level in wells can be affected by tides and if the well depth is at
the same level as the area where saline and fresh water are somewhat mixed (brackish water), then the tides might have a small influence on the
salinity of the brackish water. But, for water-supply wells, you won't find many that are tapping water at the point where saline water and freshwater mix; hopefully the well would be tapping the freshwater above the saline-water layer. In that case, freshwater would be always be accessed, despite the tides.
Wells are drilled along the coasts and they do yield great amounts of freshwater. For example, there are huge paper mills on the coast of Georgia,
and they use a lot of fresh groundwater. Since aquifers exist in generally horizontal layers below the land surface, that means freshwater aquifers
can extend underneath the oceans. Drilling a well near the coast can still tap a freshwater aquifer.
Saline aquifers also exist both underneath the oceans and under the land surface. If a well happens to be drilled into a saline or brackish aquifer,
then the well can yield saline water (which neither you nor an orange tree would like to drink). Saltwater intrusion also can be a problem along
the coasts. This can occur if a freshwater well is pumped too intensively for natural freshwater recharge from the surface to replenish it. In this
case, salty water then can be drawn toward the well opening in the aquifer, thus yielding a mix of freshwater and saline water.
11.FALSE This is false. Any water users will tend to use the water they can get to easier, cheaper, and with the least impact on the environment.
In terms of water use, public supply refers to water used by organized groups of people—such as towns, cities, and communities. During 2005,
the Nation withdrew about 29,600 million gallons per day (Mgal/d) of surface water for public-supply uses as compared to about 14,600 Mgal/d
of groundwater. Chances are that the water in that water tower on top of the hill near your house is full of water from a river, lake, or reservoir
rather than groundwater.
Now, it is true that if you dipped a jar into a creek and compared the water to water from a well, the groundwater would look a lot cleaner. The
water probably would be a lot clearer (unless there is a lot of dissolved iron, which would turn the water brown) and you would not find floating
leaf particles in groundwater. Actually, however, groundwater usually has more dissolved minerals and substances in it than surface water.
Groundwater spends a lot of time moving through rocks underground—sometimes thousands of years. Water is also the top dog when it comes to
being able to dissolve substances. Groundwater will often have more dissolved substances than surface water will.
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Ground Water Answers
12. TRUE This is true! You might think that in comparison to a mighty river, a well is a small and insignificant thing, but that well can have a
noticeable effect on a river's flow. There is more of an interaction between the water in lakes and rivers and groundwater than most people think.
Some, and often a great deal, of the water flowing in rivers comes from seepage of groundwater into the streambed. Groundwater contributes
water to streams in most physiographic and climatic settings. The proportion of stream water that comes from groundwater inflow varies according to a region's geography, geology, and climate.
Ground-water pumping can alter how water moves between an aquifer and a stream, lake, or wetland by either intercepting groundwater flow
that discharges into the surface-water body under natural conditions or by increasing the rate of water movement from the surface-water body
into an aquifer. A related effect of groundwater pumping is the lowering of groundwater levels below the depth that vegetation along the stream
needs to survive. The overall effect is a loss of vegetation and wildlife habitat alongside the river.
13.FALSE This is false. Most wells are indeed "shallow," although shallow is a relative term. Wells that produce water for peoples' uses are
generally from dozens to hundreds of feet deep—you will not find many production wells that go down 5 miles!
Not that it can't be done, though. Water can indeed be pumped from below 500 feet, even if multiple pumps at different levels have to be used. It
is true that it will cost a lot more to drill and maintain a deep well compared to a shallow well, so there is more incentive to find aquifers closer to
the land surface. But, it comes down to economics. If water is valuable (and scarce) enough, then it can make economic sense to spend the money
to pump deep water to the surface.
14. FALSE This is false. Have you ever heard this myth about groundwater? "There are rivers of water flowing below ground." For the most
part, it really is a myth. Of course, it is true that there are caverns, lava tubes, and large fissures in the ground, and some of these spaces have water in them ... ever hear of "cave diving"? A river can indeed disappear into the ground.
These hydrogeologic formations, however, are not used to supply well water. Why do all the work to find a cave full of water when there is
plenty of water in the aquifers all over (under, actually) the Earth? The most productive wells tap highly porous and highly permeable aquifers
that have a reliable source of recharge. Think of a swimming pool filled with a huge sponge (highly porous and permeable), with a garden hose
constantly keeping the pool full. If you put a big straw into the sponge, you could drink water out of it indefinitely, as long as you didn't drink
faster than the garden hose refilled the pool.
15. FALSE This is false, although a cone of depression is an actual hydrologic term. In a different sense, this is true, remembering how my
young daughter complained when her ice cream fell off her cone onto the pavement once.
All pumped wells, to varying degrees, cause cones of depressions to form around the well casing at the water-table (the altitude, below ground,
where below it the ground is saturated with water). If large cones of depressions form then the level of the water table can decline below the
depth of the water intake for the well, and the well will pump less water and possibly go dry. If this happens, it will take time for the aquifer to
recharge enough to raise the water level back to previous levels. That is why it is important to study the recharge characteristics of the aquifer
that is tapped by a well—the well operator should not pump a well faster than it is recharged, as a cone of depression could form.
Teachers should visit http://ga.water.usgs.gov/edu/quizgw.html for additional information of this subject.
Credits:
U.S. Geological Survey
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Water Efficiency
Efficient Water Technologies Lesson
Materials Needed:
·
Handout: Water Fixtures Worksheet (one copy for every two students)
·
Internet access for each pair of students
In this lesson, students examine a variety of water efficient fixtures that can be utilized in homes and schools. By exploring an interactive website, students learn about the technology of how these fixtures work and compare them with their
inefficient counterparts. Afterward, students determine which water-saving fixture would be most beneficial in reducing
water use in their homes and in their school.
Objectives:
Students will predict the areas of greatest water use in their school
·
·
Students will examine efficient and inefficient water fixtures and explain how they work.
Students will determine which water-saving water fixtures would be most beneficial for their home and for their
school.
60 Minutes
In this lesson, students examine a variety of water efficient fixtures that can be utilized in homes and schools. By exploring an interactive website, students learn about the technology of how these fixtures work and compare them with their inefficient counterparts.
Afterward, students determine which water-saving fixture would be most beneficial in reducing water use in their homes and in
their school.
Objectives
Students will predict the areas of greatest water use in their school.
Students will examine efficient and inefficient water fixtures and explain how they work.
Students will determine which water-saving water fixtures would be most beneficial for their home and for their school.
Background
On the market today there are hundreds of efficient technologies that save both money and precious resources. From aerators to dual
flush toilets, there are technologies that drastically reduce the water needs of buildings. When considering the replacement of fixtures, there are many factors to consider including its age, cost, projected water savings, payback period, and so on. In this lesson,
students focus on the amount of water saved, and consider how they would calculate these other factors if considering one or more
efficient fixtures for their school.
Advance Preparation
You will need computers with internet access for the Activity. Spend some time familiarizing
yourself with the website and all of its components, which can be found
at: http://www.greeneducationfoundation.org/water
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Credits:
Green Education
Foundation (GEF) on
Behalf of American
Standard
Water Efficiency
Do Now
Have students respond to the following question in their notebooks: In what areas of the school do you think we use the most water
and why?
Mini-Lesson
1. Place students in pairs and have them share their Do Now responses with their partners. Invite volunteers to share their responses
with the class.
2. Tell students that they are going to learn more about water fixtures that are used in their homes and their school. They will explore the technologies behind these fixtures, and compare and contrast inefficient water fixtures with more efficient ones.
3. Continue your discussion by asking students the following questions:
In the school areas with the greatest water use, what water fixtures contribute to that use?
Where else do we use water in the school and what water fixtures contribute to that use?
Are there ways we might reduce the amount of water used in the school?
What efficient water fixture technologies have you heard about and how do they save water?
Activity
1. Explain to students they will be working in pairs on computers to explore an interactive website on different water-saving technologies available for the home and the school. They will use this information to determine how they might use efficient fixtures to
reduce water use in their homes and school. (Note: This activity focuses on the ways efficient water fixtures can reduce water use. It
is important for students to also examine the role of school policies, personal behavior, and facilities practices when considering
ways to reduce water.)
2. Divide students into pairs and distribute Handout: Water Fixtures Worksheet. Point out that they need to select either the school
or home portion to see the related water fixtures around the building. By clicking on the different water fixtures they can learn about
the available technologies, their benefits, and how they work. Show them that clicking on the “How it Works” button takes them to
a video that explains how that particular technology functions.
3. Monitor pairs as they work and complete the handout. Allow adequate time – about 20 or 30 minutes – for pairs to fully explore
the interactive website.
4. Facilitate a class discussion in which students share their responses to the handout. Use the questions on the handout to guide the
discussion. Allow multiple pairs to share their answers and encourage pairs to share why they selected the technologies they did.
Assessment
Have the class create a “human bar graph” to show which efficient water fixtures they think would be most beneficial for the school.
Begin by writing the names of the efficient fixtures, evenly spaced across the front of the board. Then, have students stand in front
of the fixture they would choose. If a student is already standing there, they should create a “bar” by standing in front of that student. Have students note the most popular choice on their human bar graph and invite volunteers to explain the results based on
their discussion earlier in class.
Homework
Have students select one water-saving fixture that they would like to consider for their home and write a paragraph explaining why
they chose that technology.
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Water Efficiency
Name___________________________________ Date_________________________
Handout: Water Fixtures Worksheet
Explore the interactive website on water fixture technologies for the home and school at:
http://www.greeneducationfoundation.org/water. Then answer the questions below.
1. What are some water efficient options for each of the following fixture types?
A. Toilet:
B. Urinal:
C. Shower:
D. Dishwasher:
E. Water Fountain:
F. Faucet:
2. Which of the water-saving fixtures or technologies do you feel would be most beneficial to your school and why?
3. How much water could be saved over the course of a year if the school purchases this product? Explain how you
would determine this figure.
4. After exploring the “How it Works” videos, select one and explain in your own words how the technology works.
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