Ditches--A Simple, Inexpensive Way to Improve Surface Water Quality

A first-of-its-kind study of the transport and fate of two pesticides in vegetated agricultural drainage ditches suggests ditches are valuable tools for reducing the amount of chemicals entering bodies of water.

Drainage ditches are a common feature in the agricultural landscape. They carry runoff water from fields following storm events or controlled water releases in the case of rice fields.

Agricultural Research Servicescientists Matt Moore, Sammie Smith and Charlie Cooper at the National Sedimentation Laboratory, Oxford, Miss., evaluated the role of edge-of-field best management practices in preventing potential agricultural contaminants from entering water bodies. They simulated storm runoff events by injecting a liquid agri-chemical formulation into a drainage ditch in the Mississippi Delta.

The drainage ditch is located in the Beasley agricultural drainage area in Mississippi, one of three watershed/lake combinations being studied as part of the Mississippi Delta Management Systems Evaluation Area (MD MSEA). The MSEA project is a national effort by the U.S. Department of Agriculture to protect America's farmlands. It's designed to test and develop farming methods that will work with nature, instead of damaging water quality.

The scientists calculated the percentage of runoff that the ditch may be exposed to during a small storm (0.25 inches), looking to pinpoint its role in keeping irrigation water and pesticides from entering water bodies. They found that the ditch trapped 60 to 90 percent of the atrazine and a commonly used insecticide, Karate, carried in runoff water.

The ARS researchers say ditches may give farmers a simple, low-tech and inexpensive solution to improving surface water quality. Ditches can play an important trapping and processing role.

Through their vegetation and soil, ditches work like wetlands to sequester these storm runoff materials, thereby decreasing potential harm to downstream lakes, rivers and streams. Farmers and conservationists who want to reduce the amounts of chemicals, nutrients and sediment leaving agricultural fields may find that using and maintaining these ditches is vital as an alternative management practice.

ARS is the chief research agency of the USDA.

Scientific contacts: Matt Moore, Sammie Smith, and Charlie Cooper, ARS National Sedimentation Laboratory, Oxford, Miss., phone (601) 232-2955/2935; fax (601) 232-2915; [email protected], [email protected], [email protected].