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| Groundwater Resources of the Edwards Aquifer,
Texas |
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| Complete the questions
below by typing the answers in the boxes and printing the finished form
or print the form and write the answers in by hand. |
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| The Edwards Aquifer is located in a region
of rapid population growth centered on the city of San Antonio with
a current population of approximately one million people. The aquifer
is the major water source for an area that has been affected by long-terms
(multiple years) droughts this century. Future growth may make it impossible
to continue to divide the aquifer's waters between recreation, agriculture,
domestic supply, industry, and wildlife.
Gregg Eckhardt's prize-winning Edwards
Aquifer website provides an excellent summary of the geology of
the aquifer system and associated water supply issues. Visit the website
and answer the questions below.
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- Water levels in the aquifer are influenced by precipitation.
What is the average annual precipitation for the region?
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- Why is the average precipitation not very useful
in planning water use strategies? Describe how precipitation varies
with the climate of the region.
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- What is the rock type of the aquifer?
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- How does rock type influence porosity and permeability
in the aquifer? (Describe how is water stored in the aquifer and
how it moves through the aquifer).
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- How does water enter the aquifer at the recharge
zone?
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- Is the Edwards aquifer an open or closed aquifer?
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- Name a rock unit (and include rock type) that
lies adjacent to the aquifer that represents an aquiclude.
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Water levels in the aquifer will not decline
as long as the recharge exceeds the amount of water withdrawn from the
aquifer by pumping and by spring flow. Recharge will decline during
periods of drought. Spring flow decreased during a multi-year drought
in the early 1950's. Examine the graph below and answer the question
that follows.
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Variations in recharge, spring outflow, and discharge
by pumping form the Edwards aquifer from 1938-1992.
Graph modified from Sharp & Banner, 1997, GSA
Today, v.7, p.1-9.
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- Compare the pumping discharge to aquifer recharge
values. For approximately how many years would 1992 pumping discharge
have exceeded recharge during the time interval represented by the
graph?
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- Review information presented at the Edwards
Aquifer website and describe any two environmental issues concerning
the use of the aquifer that must be resolved in the future.
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| Return to
the Groundwater & Wetlands: Quiz & Exercises |
