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Water: Nonpoint Source Success Stories

Louisiana Section 319 Success Stories, Vol. III

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Bayou Plaquemine Brule:
Louisiana Applies Satellite Imagery to Watershed Planning & Management

 

As states continue to implement watershed planning and management strategies, several analytical tools are necessary to classify the types of land use present in each watershed. One tool that has become important for Louisiana's Nonpoint Source Management Program is satellite imagery. The images provide so much detail on the watershed that the people involved with developing management strategies, educational programs, monitoring designs, or mathematical models can clearly see what needs to be done. The maps are also very important for educating farmers, landowners, and public officials about what a watershed is and the complexity of land use patterns. The visual image seems to provide a basis for all of the people involved in watershed planning and management to begin to understand what steps will be necessary to implement best management practices (BMPs) and reduce nonpoint source pollution loads that are affecting water quality.

Pilot watershed project

The pilot watershed project where this geographic information system (GIS) tool was initially used was Bayou Plaquemine Brule, a bayou that flows through the Mermentau River Basin in southwestern Louisiana. This is rice and crawfish country, rich in Cajun heritage and traditions that have existed since the 1700s. Bayou Plaquemine Brule is on the state's 303(d) list of impaired waters and is not meeting the designated uses for fishing or swimming. The high sediment and organic loads that enter the water body each spring affect the dissolved oxygen concentrations and cause the water body to fail to meet water quality standards. The Louisiana Department of Environmental Quality (LDEQ) prioritized the Bayou Plaquemine Brule for a Total Maximum Daily Load (TMDL) in 1998 and completed all of the sampling and modeling involved to develop the TMDL by December 1999. The results of the TMDL study indicated that a 50 percent nonpoint source load reduction was needed in the upper tributaries of the bayou and a 30 percent load reduction was needed in the main stem.

Application of GIS to land use classification

To allocate this pollutant load to the various types of land uses or crops in the watershed, more detailed information was needed on land use patterns. LDEQ's GIS Center agreed to tackle this complicated task by purchasing and classifying Landsat 5 Thematic Mapper satellite imagery of Bayou Plaquemine Brule. Before the imagery could be classified, a multi-temporal data set had to be created from three separate scenes of source satellite imagery. The resultant data set was classified, producing a map of Bayou Plaquemine Brule that contains land use data for all of the major crops grown in the watershed during the 1998 growing season. This map was the result of a year of coordinated effort among numerous individuals and included extensive amounts of both lab and fieldwork. Furthermore, interagency cooperation was essential to the success of this project and resulted in a maximization of all available resources. Agencies involved included the Louisiana Department of Environmental Quality; the Louisiana Department of Agriculture and Forestry, Office of Soil and Water Conservation; the U.S. Department of Agriculture (Farm Service Agency and Natural Resources Conservation Service [NRCS]); the Acadia Parish Soil and Water Conservation District; and the St. Landry Soil and Water Conservation District.

Watershed modeling and monitoring

Once the land use classification was completed, LDEQ's Nonpoint Source Unit began work with the NRCS and the Agricultural Research Service on an agricultural watershed model called AnnAGNPS. This watershed model is being used to predict the amount of water and sediment transported through the watershed and to assist in identifying "hot spots" of high pollutant loading. The model also allows LDEQ to predict the effectiveness of BMPs that have been recommended for reducing pollutant loads to the bayou from rice, sugarcane, and crawfish farms. The result is that LDEQ is now working with Louisiana State University's Agricultural Center, NRCS, and the local Soil and Water Conservation District on a comprehensive watershed implementation strategy that will be implemented over the next 3 years. The water bodies will be carefully monitored as BMPs are implemented to track the water quality response to implementation of the practices. As these data are collected, they will be shared with the farmers so that they can know whether their efforts have been successful. Local meetings with the farmers are being held to inform them of the watershed effort and ask for their support.

Future activities

LDEQ has prioritized five additional watersheds for this type of intensive watershed planning and management. Each of the watersheds is in a different part of the state, where the soils, hydrology, land use patterns, and water bodies function differently. The goal is to have a broad database that can be used throughout the state and guide future watershed planning and management in each of the watersheds where the water body is not fully supporting the designated uses. This type of comprehensive watershed planning effort requires many partners, including local universities, educators, landowners, and resource agencies, but it results in an effective process for understanding how watersheds function and how water bodies can be improved through long-term management. 
 
Contact:
Jan Boydstun
Louisiana Department of Environmental Quality
P.O. Box 82215
Baton Rouge, LA 70884-2215
225-765-0773
jan_b@ldeq.org
Primary Sources of Pollution:

agriculture (croplands)
Primary NPS Pollutants:

sediment

organic loads

alternative livestock exclusion practices (pumps, electric fencing)
Project Activities:

GIS map of land use classifications
Results:

agricultural watershed model to identify "hot spots" of high pollutant loading and predict BMP effectiveness
 

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Flat River and Red Chute Bayou Watersheds:
BMPs Reduce Soil Loss

 

Land use in the Flat River and Red Chute Bayou watersheds consists of 25,515 acres of agricultural cropland, 29,348 acres of pastureland, and about 50 farms with an average size of 200 acres. The 1998 National Water Quality Inventory (305(b) report) indicates that the two waterbodies only partially meet their designated uses because of nutrients, siltation, organic enrichment, habitat alteration, and pathogen indicators. Soil erosion is a major problem in the watershed, as well as nutrients related to fertilizer usage.

A 319 project was initiated in the watershed to address the impacts of soil erosion. For this project, 1,100 acres of pastureland and 600 acres of row cropland were selected to install grade stabilization structures and implement best management practices (BMPs). Education regarding land-use practices was also emphasized through field days, agency cooperation, and spreading the word through the farm community to influence other landowners in the watershed to use these practices.

Installing grade stabilization structures and implementing BMPs have significantly reduced soil loss to the watershed. The reduction of soil loss for this project was calculated using the Revised Universal Soil Loss Equation. The result was a soil loss savings of 4,120 tons. Stabilization structures alone saved 595.4 tons of soil; 2,589 tons of soil were saved on pastureland; and 936 tons of soil were saved on the row cropland.

The project will continue until September 2001 and will add four new grade stabilization structures and BMPs on more pastureland and cropland. In addition to the 319 project, other programs have addressed environmental concerns in the watersheds. The Environmental Quality Incentives Program (EQIP) encompasses 5,077 acres, and the Wetlands Reserve Program (WRP) encompasses 3,500 acres in the watersheds. These two watersheds are scheduled for data collection through the 5-year basin cyclic monitoring program in 2002.
 
Contact:
Jan Boydstun
Louisiana Department of Environmental Quality
P.O. Box 82215
Baton Rouge, LA 70884-2215
225-765-0773
jan_b@ldeq.org
Primary Sources of Pollution:

agriculture (cropland, pastureland)
Primary NPS Pollutants:

sediment

nutrients
Project Activities:

grade stabilization structures
Results:

soil loss savings of 4,120 tons
 

 
 

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