Agricultural Benefits of Salinity Control on the Red River David H. Laughlin and Ronald D. Lacewell Control of salinity offers an opportunity to increase agricultural production along the Red River of Texas and Oklahoma. However, absolute benefits and the distribution of those benefits are sensitive to the crop yield effect of SAR (sodium absorption ratio). The effect of SAR on crop yield is not well defined. This study estimates agricultural benefits of a chloride control project as $65 million, not considering any SAR effect and $117 million with an SAR effect. Further, distribution of benefits was reversed between the eastern and western portions of the study area. Salinity of irrigation water and the poten- yield reductions may occur when the SAR tial accumulation of salts in the soil constitute (sodium absorption ratio) becomes a prob- a very important problem to agriculture in lem. SAR problems arise when the percent- the Western United States any in many other age of sodium ions in the residual salts is high parts of the world [Yaron]. The effect of relative to calcium and magnesium. In gener- salinity on agricultural crops is typically ex- al, the result of high soil SAR values is low pressed as a decrease in yield associated with rain and irrigation water permeability, soil a given level of soil salinity as compared with crusting, increased soil compaction, reduced yield under non-saline conditions [Maas and germination, and, hence, reduced emer- Hoffman]. Repeated applications of highly gence and stand establishment [Gerard]. saline irrigation water and subsequent re- Thus, waters containing high salt concentra- moval of pure water by the growing plant tions may be either partially or completely often results in significant salt accumulation. precluded from use for agricultural irriga- In addition to the toxic effects on the growing tion. plant, increased soil salinity results in signifi- Projections of increased worldwide de- cant reduction in water uptake by the plant mands for food and fiber through the coming and thus inhibits plant growth and reduces decades increasingly focus attention on the yield [Longenecker and Lyerly]. Further need to increase agricultural output [Hjort]. Reduction of salinity levels of irrigation water David H. Laughlin is Assistant Professor in the Depart- in portions of the Southwest can increase ment of Agricultural Economics at Mississippi State agricultural output of that region. However, University and Ronald D. Lacewell is Professor in the significant reduction of salinity concentra- Economics at Texas A&M Department of Agricultural tions in irrigation water may require substan- University. tial capital investment. To attract the needed Technical article 17081 of the Texas Agricultural Experi- capital investment, the contribution of salini- ment Station. This research was funded in part by the ty control for irrigated agriculture must be Corps of Engineers, Texas Water Resources Institute, demonstrated. and Texas Agricultural Experiment Station. The authors are most grateful to Don Moore, Rod Martin, Jack The economic importance of agricultural Runkles, Bob Taylor, Bill Harris, and John Sparlin for irrigation to the Western U.S. has been es- assistance in collecting and organizing data, developing tablished by numerous articles and publica- procedures, and generally providing many of the compo- tions on the subject, e.g., [Adams, et al., to complete this study. The authors also nents required Casey et al., Condra, et gratefully acknowledge the comments and suggestions of Mapp and Dobbins, Dow Welch and three anonymous reviewers. al., and Lacewell and Condra], for example. 195 December 1981 Western Journal of Agricultural Economics Only a few, however, have investigated the among groups of beneficiaries in the various effects and shown the economic importance geographic sections of the study area. of saline irrigation water on agricultural pro- duction. Yaron and Olian investigated man- The Study Area agement strategies to deal with salinity prob- The Corps of Engineers originally lems in a firm-level model for Israeli produc- separated the Red River Basin between Tex- tion conditions. McFarland investigated the as and Oklahoma into 15 evaluation reaches intertemporal effects of saline ground water containing a total of over 666,000 acres of intrusion for a coastal region in Mexico. An- irrigatable land. The Reaches consisted of derson and Klienman report a study for the varying-length strips of land 1.5 miles wide Colorado River basin somewhat similar to the on each side of the Red River and its major reported herein. The Anderson and one tributaries. Each reach was further sub- Klienman study, however, was designed to divided into three zones, the outer borders of help evaluate the impacts of salinity manage- which were respectively 0.5, 1.0, and 1.5 ment options for the Colorado River and miles from the river. Figure 1 illustrates the the damages that occur through- determine Corps of Engineers' original study area speci- regional economy. out a fication. Below Lake Texoma, a major mul- The Red River of the South in Texas and tipurpose lake in the approximate geographic Oklahoma is an area in which the salt pollu- center of the basin, there is sufficient dilution tion is "point-source" and to a large extent of the river water so that the salt pollution is can be controlled. About one-third of the salt not a measurable irrigation problem. Hence, pollution in the Red River is brine from local only reaches west of Lake Texoma (5-15) oil fields. The remaining two-thirds comes were applicable. from 10 salt water springs located in the Among those reaches included, the salinity River Basin in Oklahoma and salt upper Red level of the river water varied significantly, located in Texas [Department of the seeps depending on the reaches' proximity to salt Corps of Engineers has submit- Army]. The sources, hence causing varying levels of crop a plan to construct a system of subsurface ted yield reduction. In general, river water in shallow wells, and collection cut-off walls, the far western reaches (10, 11, 13, 14, and reservoirs to collect and dispose of much of 15) has higher salt concentrations than does source salt waters. As a result, water from the that in the eastern reaches (5, 6, 7, 8, 9 and Red River would be made usable for the 12). Therefore, the opportunity for increased irrigation, though still not com- agricultural crop productivity, and, hence, net project free of salts. The primary purpose of pletely benefits, was expected to vary among reaches study reported herein was to determine the depending upon both the salinity level and agricultural benefits of a pro- the potential on the inherent productivity of the soils in chloride control project posed Red River each reach. [Laughlin, Lacewell and Moore]. Results of suggest that the SAR [Gerard, et al., 1979b], Procedure of irrigation water from the Red River is of considerable importance for soils similar to The estimation of potential economic ben- those in the Red River Basin. However, efits to agriculture from the Red River SAR-induced crop yield reductions are not Chloride Control Project was the second conclusively established for the Red River component of an overall agricultural study for Basin. A second purpose and major objective the project. Soil scientists, agronomists, en- of this paper was to investigate the expected gineers, and irrigation specialists teamed in impact of salinity and SAR-induced yield re- the first part of the study to provide the many duction on the salinity control project bene- agronomic and hydrologic relationships that fits and the distribution of those benefits were necessary for the development of an 196 Laughlin and Lacewell Benefits of Salinity Control OKLAHOMA ARKANSAS - CountyLine ""- River ReachBoundary ( Reach Number Figure 1. Map of the Study Area. adequate economic model [Grossman and Irrigation water requirements for each Keith]. Data provided by the physical scien- crop were based on "average" consumptive tists for each evaluation reach included: (1) use of water for each crop. Average consump- irrigation water requirements for each crop tive use calculations for each crop were based grown in the study area, adjusted for normal on methodology used by McDanields. Con- precipitation and leaching requirements; (2) sumptive use estimates of water which would reduction in yield attributable to the chloride need to be supplied by irrigation were fur- concentration with and without the project; ther refined by consideration of effective av- (3) acreages in each zone and reach potential- erage monthly precipitation differences ly suitable for irrigation (classified by soil among reaches.l In addition, a 20% leaching type, slope, and land capability class); (4) fraction was assumed to be the standard prac- recommended irrigation systems for each soil tice [Gerard et al., 1979a]. Further, irriga- type (furrow, border, or sprinkler); and (5) tion system efficiency rates of 75 and 85 current acreages of major crops. Further, percent for sprinkler and surface systems, estimates of the amount of water available for respectively, were used to adjust the total irrigation from the Red River alluvium, by amount of irrigation water that must be reach, were provided by the Corps of Engi- pumped to account for losses within the wa- neers. ter distribution system. Of the items listed above, the information Reduction in crop yields attributable to in items 3 through 5 require substantial time chloride concentrations of the Red River irri- and effort to determine, but their determi- and subject to nation is rather sraightforward 1Effective rainfall for the different reaches was estimated little controversy. Items 1 and 2, on the other using U.S. Department of Agriculture Soil Conserva- hand, are critical to this analysis and are tion Service Engineering Division Technical Report worthy of further explanation. No. 21 [Gerard, et. al., 1979a]. 197 December 1981 Western Journal of Agricultural Economics gation water with and without the project based on a 100-year (years 1990-2090) plan- and with and without SAR crop yield effects ning horizon using OBERS Series E' [U.S.