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<br />f I were an early settler
<br />traveling to the west, bouncing
<br />and rattling along in my wagon,
<br />through the Sand Hills of Nebraska,
<br />parched and dusty, I would be
<br />ignorant of the fact that I was
<br />traveling on dry land but over an
<br />ocean of fresh water. ®galla]
<br />But I am a modern
<br />traveler, and only a few
<br />weeks ago I was cruising
<br />comfortably along I-80 Wyoming.
<br />across those same Sand
<br />Hills of Nebraska on my
<br />way to the Annual Gem,
<br />Jewelry, Mineral, and Color<
<br />Fossil Show in Denver,
<br />Colorado. As I traveled
<br />across Nebraska I passed
<br />through Grand Island, New Mex'
<br />Kearney, Lexington,
<br />North Platte, and the
<br />town of Ogallala before
<br />swinging southwest to Denver.
<br />I stopped in Ogallala because it
<br />represented part of the northern reach
<br />of the gigantic Ogallala Aquifer, also
<br />known as Great Plains Aquifer. This
<br />tremendous buried source of fresh
<br />water begins in south-central South
<br />Dakota, covers most of Nebraska, and
<br />then trends southward through
<br />western Kansas, eastern Colorado,
<br />northern Oklahoma, eastern New
<br />Mexico, before winding up in Texas- a
<br />total area of 104.5 million acres or
<br />225,000 square miles. The area is an
<br />800 mile stretch of green lushness,
<br />made possible by the discovery of the
<br />vast source of underground water plus
<br />modern irrigation techniques. One
<br />observer labels the Ogallala Aquifer as
<br />"upside-down rain". A Nebraska State
<br />Senator has said, "without irrigation,
<br />Nebraska's gross product would
<br />decrease by 70%". Irrigation in the dry
<br />western U.S. can produce as much as
<br />three to four times more crop than dry
<br />land farming.
<br />An aquifer is any geological
<br />formation containing or conducting
<br />ground water, especially one that
<br />supplies water for wells and springs.
<br />This spectacular Ogallala Aquifer is
<br />Aquifer like a giant sponge,
<br />soaking up moisture
<br />from mountain-runoff
<br />South Dakota in the West, where
<br />_ ~ rainfall varies from a
<br />- few inches to more
<br />~`~'~'~"~"~ ~~ "` than 20 inches per
<br />-_ ~
<br />~--=. year and low
<br />~ `:" j ~" humidity creates
<br />1 ~:a?is'.~s
<br />~..~~ _ high evaporation
<br />,.; _,
<br />-+`' -.._~•-., rates. The
<br />~ ~ ~ ' -" a uifer is
<br />f = '' :- `Oklahoma q
<br />'' composed of
<br />remnants of
<br />~ ` Texas erosion of the
<br />high
<br />mountains to
<br />the west.
<br />Because the
<br />aquifer covers an
<br />immense area and its
<br />thickness varies as well as the
<br />composition of the formation, the rate
<br />at which the water recharges is highly
<br />variable. Geologists have determined
<br />the area over which I recently drove to
<br />have the highest rate of recharge in the
<br />entire reservoir. I have often
<br />wondered why the Sand Hills area of
<br />Nebraska has sb many ponds, small
<br />lakes, and water standing in most
<br />ditches, while surface soils and the
<br />rolling hills are sandy, requiring
<br />irrigation for farming.
<br />The mystery was solved, at least
<br />partially, by a report by the Playa Lake
<br />Association. Playa lakes are shallow
<br />wetlands with clay bottoms lying in
<br />the lowest point of a large enclosed
<br />watershed. The surface of the Ogallala
<br />Aquifer is dotted by 60,000 playa lakes,
<br />especially in the Nebraska area. These
<br />playa lakes are the main source of the
<br />natural recharge of water, as
<br />precipitation percolates through the
<br />soils and underlying sediments to the
<br />water table.
<br />The Ogallala formation itself is a
<br />hodge-podge of sand and gravel, with
<br />pebbles and boulders varying in size
<br />but becoming smaller and smaller as
<br />the formation spreads to the east. This
<br />fact is evidence that the source of
<br />materials in the formation was the
<br />erosion of mountains to the west.
<br />Water withdrawal from the aquifer
<br />became a severe problem during the
<br />drought of the 1930s, especially in Texas
<br />where growth of cotton flourished with
<br />irrigation. Many studies and use
<br />projections show that the water in the
<br />Ogallala is finite and careful planning is
<br />essential to preserve the precious water
<br />for future generations.
<br />As of today, it seems a reasonable
<br />balance has been obtained, although
<br />climatic variations over such a large
<br />area often create water level drops
<br />that cause concern. But, scientists
<br />monitor water levels carefully and the
<br />impacts associated with climatic
<br />changes due to global warming are
<br />evaluated closely. Even an invisible
<br />ocean of water can be affected by
<br />global warming.
<br />~`~G ~r~
<br />
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<br />'~'" FACETS October 2005
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