Changyoon Jeong and Ernest Girouard

Because Louisiana occasionally experiences severe seasonal droughts, it is important for farmers to develop dependable sources of irrigation to meet crop needs for water during critical stages of growth. Local communities have been looking for alternative irrigation strategies to conserve groundwater and use more surface water for irrigation. The Red Bayou Watershed project started as an effort to use the Red River as a dependable source of surface water for irrigation by pumping water from the Red River to the Red Bayou for use as irrigation water in northwestern Louisiana near Gilliam (Figure 1). The project, which was started in May 1997 and completed in September 2014, was supported by the Natural Resources Conservation Service (NRCS), as well as several local partners including the LSU AgCenter Red River Research Station.

Since the start of the project, the quality of the water for use in irrigating crops has been tested at five sites along the Red Bayou. Water quality monitoring is essential in determining the suitability of water for irrigating crops and the effects of agricultural watersheds in this unique water management system. Water samples were collected every week during the crop growing season and once a month in the off-season from the five monitoring locations. During water sample collection, a smarTROLL multi-parameter measuring device made by Colorado-based In-Situ was used to measure parameters including water depth, dissolved oxygen, pH, temperature, electrical conductivity and turbidity.

Long-term water quality monitoring to monitor water quality in watersheds is expensive and time-consuming. Modeling techniques can be an alternative way to simulate the magnitude of contaminants and to develop a decision-making tool in watershed management systems. The Soil and Water Assessment Tool (SWAT) model was selected for predicting long-term water quality in the Red Bayou watershed.

Two years of monitoring data showed a strong seasonal and spatial variation in surface water quality across the Red Bayou watershed due to the influence of weather and local agricultural activities. In the SWAT model application, a good agreement (R² = 0.66) was obtained between the observed and simulated phosphorus concentration in the validation process as a selected parameter (Figure 2). The significance of this study was to provide an overall understanding of the impact of irrigation and agricultural practices on water quality in the Red Bayou. Further research is required to assess the impact on the accumulation or movement of salts, carbon, nitrogen, phosphorus and other micronutrients on water quality in irrigated crop fields.

Changyoon Jeong is an assistant professor at the Red River Research Station in Bossier City. Ernest Girouard, now retired, was the coordinator for the Louisiana Master Farmer Program.

The two pumps behind Changyoon Jeong, an assistant professor at the Red River Research Station in Bossier City, send water from the Red River into the Red Bayou so local farmers can use it for irrigation. The bayou is located in the Gilliam area of northern Caddo Parish. The pumping system is part of a Natural Resources Conservation Service project aimed at increasing the use of surface water sources, such as the bayou, for irrigation and lessening the strain placed on groundwater. Photo by Olivia McClure

Figure 1. The quality of the water for use in irrigating crops has been tested at five sites along the Red Bayou near Gilliam, Louisiana.

The Natural Resources Conservation Service Red Bayou Watershed Project in Caddo Parish is giving farmers a nearby source of surface water for irrigation. Water is pumped from the Red River into Red Bayou, which cuts a narrow path through vegetation. LSU AgCenter scientist Changyoon Jeong monitors water quality at this site and several others along the Red River and Red Bayou. Photo by Olivia McClure

Figure 2a. The trend of soluble reactive phosphorus concentration from the Red Bayou watershed.

Figure 2b. SWAT model simulation with observed data at Site 5.