The sandstone in the picture is permeable.
Permeable means that the substance can hold water, kind of
like a sponge.
Impermeable means that the substance cannot be penetrated,
like a tabletop.
Not all rock is impermeable;. Some sandstones act like a
really slo-o-o-w moving sponge, taking thousands of years to
let water percolate (like a coffee pot) through them. The
Ogallala aquifer water is 12,000 years old, and it took the
melting of the Ice Age to fill it!
Groundwater is extremely important. It is where we get a good portion of our freshwater.
There is more groundwater than all the lakes and streams put together. Groundwater is also
polluted more than all of the other sources of fresh water.
Groundwater starts on the surface. When it rains and the water moves through the soil it's called
INFILTRATION.
When the water can go no deeper, it creates an AQUIFER. An aquifer is an underground
reservoir inside the rocks. When a farmer digs a well, they are digging into an underground
aquifer. After they drill to the WATER TABLE (the highest level of the aquifer) they are able to
pump the water to the surface.
During the 1930’s, farmers discovered a huge aquifer that contained what seemed to be unlimited
water. This aquifer is called the Ogallala Aquifer, and covers parts of Wyoming, South Dakota, Nebraska,
Colorado, Kansas, New Mexico, Oklahoma & Texas. Crops flourished, farmers were happy. After World
War II, the population of the United States started growing very rapidly, and during the 1960’s, farmers
learned how to use circular sprinkler systems that helped the crops to grow even better, using a lot more
water. There is about a quadrillion gallons (1,000,000,000,000,000) of water in the aquifer.
The Ogallala Aquifer will last about another 30 years at present rate of usage.
The Ogallala has begun to
show its limits. Although the
aquifer is still the largest
underground water source in North
America, water is being withdrawn
about 40 times faster than it is
being replaced. That means that if
40 cans of water are withdrawn,
only 1 is replaced. Most of the
water is used for irrigation, and in
some places the water level has
dropped more than 100 feet since
pumping began. Many people have
had to stop using their wells
because it was too expensive to dig
them any deeper.
Farmers have begun to use
conservation measures to reduce
the amount of water they use, but
the problem persists.
Working in Pairs or Alone,
Using the data found in the article and the table below, plus your own knowledge and common sense,
answer the following questions.
1. Why is groundwater more polluted than surface water?
2. Why can’t the Ogallala Aquifer be refilled by watering its recharge zone? (Where the water
enters).
3. How many millions of gallons are being withdrawn per day from the Ogallala Aquifer?
4. Rank the states from most to least users of the Ogallala Aquifer’s water, and explain why each uses
what it does.
5. At present rate, how many years will it take to empty the Ogallala Aquifer?
Knowing that the world’s population is growing, and that the United States exports more food than any
other country,
6. Name three possible, workable solutions to the problem of the depletion of the Ogallala Aquifer.
7. Pick what you think is the best possible solution and describe in detail how you would put this plan
into effect.
7. Based on the your results from the Water Filtration Lab; If you were the governor of Nebraska, would
you allow Kansas to build an oil pipeline from South Dakota to Kansas if Kansas paid Nebraska $10
million dollars for permission?
Why or Why not? Defend your answer.
State
Water
withdrawals,
in Mgal/d
State
Alabama
403 Kentucky
Alaska
112 Louisiana
Arizona
2,740 Maine
Arkansas
4,708 Maryland
Water
withdrawals,
in Mgal/d
State
247 North Dakota
1,341 Ohio
85 Oklahoma
240 Oregon
Water
withdrawals,
in Mgal/d
141
904
*905
767
California
14,883 Massachusetts
338 Pennsylvania
1,023
Colorado
*2,799 Michigan
707 Rhode Island
25
Connecticut
Delaware
D.C.
165 Minnesota
282
89 Mississippi
2,674 South Dakota
*251
1 Missouri
728 Tennessee
503
Florida
4,665 Montana
Hawaii
590 Nebraska
Georgia
996 Nevada
Idaho
797 South Carolina
7,593 New Hampshire
218 Texas
*4,797 Utah
*7,877
971
1,071 Vermont
45
64 Virginia
443
Illinois
945 New Jersey
566 Washington
Indiana
621 New Mexico
*1,762 West Virginia
728
Iowa
495 New York
840 Wisconsin
681
*4,364 North Carolina
435 Wyoming
*403
Kansas
Puerto Rico
157 Virgin Islands
3
1,452