Constructing a Wetland To Improve Water Quality

Linda Benedict  |  4/5/2005 1:15:02 AM

Eddie P. Millhollon, James L. Rabb, Russell A. Anderson, Jose F. Liscano, Danny F. Martin, Steven G. Nipper, Scott D. Edwards and Richard W. Adams

Louisiana’s coastal waters, lakes, rivers and bayous are the lifeblood of the state. They have provided economic survival and year-round recreation, earning the state the well-deserved title of “Sportsman’s Paradise.”

Recognizing the need to protect the state’s most precious natural resource, Louisiana’s agricultural producers have adopted practices that aid in protecting water quality, such as conservation tillage. Although these practices reduce nonpoint-source discharges from agricultural fields into the state’s water bodies, new practices are being recognized that may offer additional improvements.

One such practice is the use of a constructed wetland, because it has long been known that the biological and physical properties of natural wetlands are beneficial in improving water.

The LSU AgCenter Red River Research Station consists of 573 acres of agricultural land in the Red River Basin of northwest Louisiana. Runoff water from the station drains into the Flat River, which is less than one-third mile away. Approximately 400 acres of discharge water from the station flows to the southeastern corner where it enters Lay’s Bayou, then Flat River.

The southeast corner of the station is, therefore, an ideal location to investigate the potential of a constructed wetland for improving the water quality of discharge from agricultural fields.

In 2003, a research team at the Red River Station was awarded a grant from the Louisiana Department of Environ-mental Quality (LDEQ) to construct a wetland at the station. The effectiveness of this system will be determined by sampling water at various points along the path of the system, from the point where runoff enters the wetland to the point where it leaves. In addition to gathering data, grant money will be used to develop and implement an educational outreach program to inform agricultural producers of the benefits that can be derived from the construc-tion of a wetland.

An area in the southeast corner of the Red River Station was surveyed by personnel of the Natural Resource Conservation Service (NRCS) to identify the best location for a con-structed wetland. The wetland consists of three sections. Runoff from 400 acres will enter the wetland through three drainage ditches. At the point where the drainage ditches enter the shallow portion of the wetland, soil will be excavated so that each will have a depth of approximately 6 feet. This depth will allow most sediment to fall out before water enters the shallow wetland.

The shallow wetland will be approximately 3 acres and range in depth from zero to 18 inches. Native aquatic plants have been collected and placed in a nursery until they can be transplanted to the shallow wetland.

From the shallow wetland, water will enter a 2.25-acre wetland that will be approximately 6 feet deep. The deeper wetland serves as a “polishing” pond that provides anaerobic conditions necessary for denitrification of nitrates and breakdown of pesticides. Water will then pass through the deep wetland to a ditch leading to the Flat River through two 48-inch culverts.

Water quality changes through the system will be monitored by three auto-matic water sampling stations. The first will be near one of the three ditches that drains run-off from the 400 acres immediately before it enters the con-structed wetland system. Samples from this location will be analyzed to deter-mine quality of water entering the constructed wetland system.

A second sampling station will be located on the levee separating the shallow and deep wetland. This station will sample water in the shallow wet-land to determine improvements in water quality at this stage of the con-structed wetland system. The third sampling station will be located at the levee that separates the deep wetland from its point of egress. This station will collect water samples from the deep wetland to determine improvements in the quality of water at the final stage of the constructed wetland system.

Construction of the wetland began in December 2003, and the system should be operational by the summer of 2004. The project is presently funded for three years. In addition to the research component of this project, there is an extension component that will provide educational programs that will demonstrate the benefits of a con-structed wetland in improving and preserving Louisiana’s precious natural resource.

Eddie P. Millhollon, Associate Professor; James L. Rabb, Professor; Russell A. Anderson, Research Associate; and Jose F. Liscano, Research Associate, all at the Red River Station, Bossier City, La.; Danny F. Martin, Civil Engineer; Steven G. Nipper, Water Quality Specialist; Scott D. Edwards, Plant Materials Specialist; Richard W. Adams, Soil Conservationist, all with the Natural Resource Conservation Service.

(This article appeared in the spring 2004 issue of Louisiana Agriculture.)

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