U.S. Water News Online
OKLAHOMA CITY -- Pesticides are getting into the groundwater in the Ogallala Aquifer faster than authorities expected, according to officials with the U.S. Geological Survey.
``The aquifer is more susceptible than we ever thought it was,'' said Bill Andrews, chief of studies for the survey's office in Oklahoma City. Andrews said experts had thought it could take hundreds or even thousands of years for materials to seep into the aquifer.
A survey of groundwater samples taken in cooperation with the Oklahoma Water Resources Board found traces of pesticides that have been in use for only 30 years.
The survey looked at well water samples from 12 sites in the Panhandle. The samples showed a median nitrate concentration of 3.5 milligrams per liter of water. For comparison, the results of 167 samples taken between 1940 and 1992 showed a median nitrate concentration of 2.3 milligrams per liter of water.
Kathy Peter, district chief of the survey, told legislators and state officials that the traces of pesticides don't mean an immediate health hazard.
``But it does tell us that pesticides are getting into the groundwater faster than we thought,'' she said.
The draft study also shows that in two of the wells sampled, nitrate concentrations were higher than what is allowed in drinking water. Andrews said the two were above the Environmental Protection Agency's recommended limit of 10 milligrams per liter and one was just below that level.
The nitrogen in two samples could be traced to animal wastes. The samples came from sites near large confined animal feeding operations.
``It's frightening to know we are having some pesticide seepage. Now we need a lot more study of percolation rates in all the aquifers in the state,'' said state Rep. M.C. Leist, D-Morris. He is head of the House Agriculture Committee.
Andrews said the pesticide traces found included atrazine, which is commonly used to raise corn in the Panhandle, and simazine and metalachlor.
The pesticides have been used over the past 30 years, Peter said.
The Ogallala is a groundwater foundation that lies beneath eight Midwestern and Western states. It supplies water for many farms, industries, and towns.
Andrews said the new study is based on only a few samples. ``It doesn't necessarily mean the whole aquifer is becoming more contaminated,'' he said.
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