How Chemicals Seep into the Aquifer
By Hank Becker
May 15, 1997
Scientists have answered one of the
questions of the Midwest: how drinking water coming from aquifers gets
contaminated with chemicals.
Walnut Creek, a tributary of the South Skunk River near Ames, Iowa, is a
typical small stream in the area. Before flowing into the river, the creek
passes over a sand and gravel aquifer.
Scientists with USDAs
Agricultural Research Service have
confirmed the movement of water through the creek bed and into the underlying
aquifer. They accomplish this by measuring water levels in the aquifer and flow
in the stream on two sampling dates. Chemical analyses of 24 water samples
showed that the water entering the aquifer contained nitrate and herbicides,
The scientists estimate that the creek could contribute substantially more
atrazine to the aquifer than leaching through a field equal in area to that of
Both the stream and aquifer conditions studied are common in the Corn Belt.
Alluvial aquifers, sometimes called buried valley aquifers, are
found near most major rivers in the region.
This type of aquifer has been found to contain the greatest contamination of
all ground water resources in the Corn Belt. Defining the stream-aquifer
connection could prove critical in explaining contamination of important ground
water resources used by communities and farmers. Implications are that managing
fields upstream may be more important than managing fields over an aquifer.
Scientific contact: Michael R. Burkart, ARS
National Soil Tilth Laboratory, Ames, Iowa,
phone (515) 294-5809, fax (515) 294-8125, email@example.com.