Linda F. Benedict, Linscombe, Steven D.
Plentiful, good quality water was one of the major attractions of southwest Louisiana more than 100 years ago when farmers who moved there to try growing rice. Later, when deep wells were drilled, it became evident the region had abundant groundwater, too. The rapid spread of rice production in southwest Louisiana was facilitated by the establishment of canal systems. Typically, these systems would be anchored by a pumping plant on a river or bayou. Most of these pumping plants had steam engine-driven pumps that could lift large volumes of water. A large irrigation canal or system of canals would then be constructed leading away from the pumping station, often for more than 20 miles. The rice fields adjacent to the canals could then be flooded. In return for water, the rice farmer would pay a percentage of rice sales to the canal company. Over the past 40 years, however, most of these major canal systems have disappeared. Their loss has necessitated the drilling of numerous deep wells to keep many fields in rice production.
Today, about 60 percent of Louisiana’s rice acreage is flooded from deep wells and 40 percent from surface water. If surface water is available, it is the irrigation source of choice because it takes much less energy to lift water a few feet from a surface water source rather than several hundred feet from a deep well.
Surface water quality and quantity has become a major issue in Louisiana rice production because of the declining rate of average annual rainfall. According to records at the Rice Research Station, the average annual rainfall over the past 100 years has been just below 60 inches. Yearly rainfall has varied, however, from a high of 106 inches in 1940 to a low of 31 inches in 1921. In just the past few years, this number has varied from a high of 73 inches in 2004 to a low of 37 inches in 1999. By mid-December 2011, it was 42 inches.
Drought conditions have left some surface water pumps on smaller drainage systems with little or no water to pump. Perhaps more important is the relationship between our watersheds and the Gulf of Mexico. Our rivers, bayous, streams and drainage ditches remove excessive rainfall and eventually dump this water into the Gulf. As this fresh water moves south, it becomes increasingly brackish as it interacts with seawater. Under normal rainfall conditions, the brackish water remains south of surface water pumps. However, under drought conditions, this high-salinity water begins to move north. Rice is a freshwater plant and will not produce well and eventually will die as salinity levels in irrigation water increase.
This is the situation in many rice production areas of Cameron, Calcasieu, Jefferson Davis and Vermilion parishes. In addition to drought, the Lehman- Bowman locks on the Gulf Intracoastal Waterway were recently damaged and will not be repaired for several months. This allows additional high-salinity water to flow north. The bottom line is that unless we receive high levels of rainfall this winter and early spring, many of these areas will not be able to produce a rice crop next summer.
While this high-salinity water is not a problem every year, it is occurring with increasing frequency. It also affects freshwater marsh holdings, waterfowl hunting, freshwater fishing, alligator egg collection and hunting, as well as the vast beef industry along the coast. Beef producers are beginning to worry about fresh drinking water for their herds.
A coalition has been formed to study long-term solutions. One idea is to divert fresh water into the region from the Mermentau River basin. The Tech/Vermilion diversion project already in place shows this can be done successfully. Any such diversion project has a many obstacles to be overcome, including the finding of funding sources.
Steven D. Linscombe, Director, LSU AgCenter Southwest Region, Crowley, La.
(This article was published in the winter 2012 issue of Louisiana Agriculture magazine.)