Computers, GIS Help Prevent Ground Water Contamination

May 28, 1998

WEST LAFAYETTE, Ind.--Surrounded by computer screens and hard drives, Bernie Engel creates and analyzes digital images that help keep Indiana ground water clean.

Engel, a Purdue University agricultural engineer, combined a computer model with geographic information systems (GIS) data from satellites to develop a plan to keep agricultural chemicals out of the ground water, which supplies the drinking water for 60 percent of the state's population. For his work, Engel received the 1998 Research Award from the Purdue School of Agriculture on May 6.

His data base and program are the first to pinpoint potential water problems field-by-field, and the first of their kind on the Internet at That Web site still is under construction, but pesticide users eventually will be able to use it as they decide how much of a chemical is safe to use on each field.

The Office of the Indiana State Chemist used Engel's system to write the Indiana State Pesticide Management Plan. The plan identifies and protects parts of the state most likely to suffer water pollution from chemical spills or from excess pesticide or fertilizer applications. Other states are modeling their plans after Indiana's, Engel said.

"[Engel's research] is certain to be one of the central agricultural engineering achievements of the 21st century. It offers the prospect for highly cost-effective use of resources and the virtual elimination of nonpoint source pollution of surface and ground water," wrote Alfred Krause and Michael Bland in a letter supporting Engel's nomination for the Purdue award. Krause is the national expert for water conservation for the U.S. Environmental Protection Agency (EPA). Bland is chief of the software development section for EPA Region Five.

Engel's methods already are used by NASA's Kennedy Space Center, the U.S. Army, the USDA Natural Resources Conservation Service and the EPA.

As its name implies, ground water lies below the earth's surface. It seeps slowly through layers of sand, soil or rock, pooling in places where people can pump it out for drinking, bathing, cooking or cooling off. "Once it's contaminated, it's almost impossible to clean up," Engel says.

So he looked for ways to protect it. From the start, Engel worked with the Indiana Department of Environmental Management (IDEM) and the state chemist, because he wanted his research to meet their needs, as well as the needs of farmers.

Both agencies were eager to work with him after analyzing ground water data assembled in 1995 by the U.S. Geological Survey, EPA and the Indiana Department of Natural Resources. Those studies found 18 pesticides and five pesticide breakdown products in 9 percent of the samples. Half the sampled wells had nitrate levels above 2 parts per million (ppm)--below the EPA action level of 10 ppm, but still a concern. The state was poised to act.

"A regulatory approach didn't make economic or environmental sense," Engel says. Across-the-board bans of certain pesticides punish farmers who could otherwise use those chemicals without risk to the environment. They also force regulatory agencies to spend money unnecessarily as they try to monitor all the ground water in the state, rather than concentrating on water that is most at risk.

"Monitoring is the most costly component of the State Management Plan," says Alan R. Hanks, the Indiana state chemist, "and it can only be decreased based on a clearly established picture of the vulnerability of ground water to contamination."

Some ground water probably never will be contaminated. For instance, soil types in one area might bind chemicals before they can reach ground water, or the water table may be so deep that contaminants likely won't reach it. However, other areas are accidents waiting to happen.

Before Engel's research, state agencies had trouble pinpointing potential problem areas.

Engel started with an existing computer model that rated pesticide contamination risks in Indiana, county by county. The model was good, but not good enough.

By combining an updated computer model with GIS data, Engel pulled together and analyzed detailed data on the state's geology, watersheds, soil types, climate and more. The combination gave Engel, and state agencies, a way to predict potential ground water hot spots.

To be sure his contamination predictions would hold water, Engel compared them to measurements of nitrate and pesticides in well water samples from across the state. His model predicted contamination problems more accurately than did any previously used technique.

Engel's model indicates that 75 percent of detectable pesticides in ground water come from 25 percent of farmland. Indiana agencies use this information to focus their monitoring efforts.

"It is now possible to gain significant savings by concentrating the most intense monitoring efforts in truly vulnerable areas," Hanks says.

The State Chemist's Office and the Purdue Cooperative Extension Service also are starting an educational campaign in high-risk areas, teaching residents how to protect their ground water.

The next step, according to Engel, is to finish putting it all together on the World Wide Web site so that farmers can enter data such as where they live, what crops they grow and which pesticides they plan to use. The computer will know the farmer's soil type, 30-year weather history, geology, watershed and more, then will figure out if the farmer's management practices put his or his neighbors' drinking water at risk. Eventually, it could offer recommendations on the least risky pesticides and farming methods.

Purdue University

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