That's a Deep Subject
by Rex Buchanan
Every January, researchers from KU's Kansas Geological
Survey, or KGS, fan out across western Kansas. For a little more than
a week, they work with the state's Department of Agriculture to measure
the water levels in about 1,500 wells.
The resulting numbers, when combined with measurements
from previous years, show changes in western Kansas water levels. Combined
with decades of measurements, the results show long-term changes in
water levels. In western Kansas, which relies on groundwater for more
than 90 percent of its water supply, and especially for the irrigation
that supports much of the agriculture, these measurements amount to
a check on the region's life's blood.
The numbers are used by irrigators to make decisions
about drilling new wells; by government agencies to regulate water use;
by banks, as they ponder loans.
The object of all this attention is the High Plains
Aquifer, an underground layer of water-bearing sands and gravels. Probably
the best known part of this aquifer is the Ogallala Formation.
When the KGS heads out to measure water levels, each
vehicle is equipped with a global position system connected to a laptop
computer. Using software written at the survey, the global position
system guides each driver to the right well. Once the well has been
measured, the results are entered into the laptop.
Actually
measuring the well, however, is decidedly more low-tech. It's like checking
the oil in a car. Researchers thread a steel tape through an opening
at the base of each well, playing out the tape to a prescribed depth.
Assuming the tape doesn't get tangled in the well's internal workings
(some wells are notoriously difficult to get a tape into and out of),
the tape is wound back up and checked to see where it hit the water
table.
(It's like looking at a dipstick to check the oil level
in a car. The height of the oil on the dipstick is a direct measure
of the level of the oil in the crankcase. However, unlike oil, water
on a steel tape can be difficult to see. To improve the contrast between
wet and dry tape, a thin coating of blue carpenter's chalk is applied
to several feet at the leading end of the tape.)
The numbers are sent back to Lawrence, where they're
compiled, analyzed and published. The water level in each well can be
viewed electronically (click
here). You can search this database by county or by legal description.
It includes thousands of wells; if you only want to view those that
have current water-level information, make sure to check the appropriate
box when you do the search.
Water specialists at the KGS also map the results to
reveal trends. Compared to the measurements made in 1997, for example,
those made in January 1998 showed small declines in northwestern and
southwestern Kansas. The average well measured in west-central Kansas
actually rose slightly.
Long-term trends, however, are far more ominous. Since
irrigation began in earnest in the 1960s, pumping has depleted from
25 to 50 percent of the saturated portion of the High Plains Aquifer
in Grant County in far southwestern Kansas. Given that the water took
hundreds of thousands of years to accumulate and is naturally replaced
at a rate so low that it's meaningless, these declines are cause for
concern.
The KGS is now working with the Kansas Water Office
on a study of the High Plains Aquifer, examining trends in water use
and trying to determine what methods -- education, regulation, economic
-- are most effective for slowing declines in the water levels.
In January 2000, the KGS was back for another round
of measurements.
Rex Buchanan
Associate Director for Public Outreach
Kansas Geological Survey
rex@kgs.ku.edu
