What do you think of when you hear the word “water”? Is it the ocean breaking on a
sandy beach? Perhaps a lake, or rain or even the water that comes from your faucets and
showers? Have you ever considered where the water you use daily comes from? For some it's
a river, others a lake, and in many places people get water from deep within the ground,
where it is mixed within the porous sedimentary rocks. Such underground water is also known
as an aquifer. An aquifer is a rock layer that contains significant
amounts of water that people can use. Such water is also called groundwater. Groundwater
stored in aquifers is used worldwide to provide drinking water and irrigate crops. Aquifers
and groundwater are especially important in regions where there is not enough rainfall
to meet people’s needs. A very interesting and important aquifer is the Ogallala aquifer,
which underlies parts of 8 US states; Texas, New Mexico, Oklahoma, Colorado, Kansas, Nebraska,
Wyoming and South Dakota. It covers 174,000 square miles, which is equal to 85 million
football fields, or about 2/3rds the size of Texas. The Ogallala Aquifer consists of
sand and gravel, with lots of space between grains that can be filled with water. One
way to describe an aquifer is by how thick the sediment layer that is filled with water
is; for some parts of the Ogallala aquifer, this reaches a saturated thickness of 1200
feet. The Ogallala aquifer formed roughly 5.3 million years ago from deposition of sand
and gravel eroded from the Rocky Mountains. The Ogallala Aquifer was first tapped on a
large scale after World War 2, when farmers got access to diesel pumps. These pumps let
them extract over 100 gallons of water per second. That’s a lot of water; compare that
to your kitchen faucet which puts out about 2 gallons per minute.So tapping the Ogallala
aquifer provided plenty of water for irrigation. The Great Plains region pumped and pumped,
changing a near-desert region into the largest agricultural region in the United States.
Most aquifers are recharged by rainwater filtering down from the surface but if depletion by
pumping is greater than the recharge, the aquifer will be depleted and ultimately exhausted.
The Great Plains is a very arid region, meaning the recharge rates for the Ogallala aquifer
are very low. With withdrawal rates up to 26 cubic kilometers per year , which is equal
to 10 million olympic swimming pools, and excruciatingly low recharge - or refill - rates
there’s a big problem. So what can be done to preserve the Ogallala?
People and communities who rely on water from this aquifer need to save and recycle water.
Farmers also need to find new irrigation techniques that water a large area using less water and
plant crops that require less water. Governments need to monitor aquifer levels and rates of
change and use this information to thoughtfully regulate how much water should be withdrawn.
Scientists need to figure out new ways to inject fresh water into the aquifer, perhaps
using river water, pipes and pumps. If we fail to better manage the water remaining
in the Ogallala Aquifer we risk exhausting it. If this happens the region will return
to the dry wasteland it once was.