Nitrate, Chloride and Dissolved Solids, Ogallala Aquifer, West Texasa

Abstract

ABSTRACTThe distribution of nitrate, chloride and dissolved solids from ground water from the Ogallala aquifer in a 27‐county area of west Texas illustrates widespread areas of poor water quality. Elements studied increased in concentration from northwest to southeast across the Southern High Plains. Northeast of a line from about Clovis, New Mexico to Lubbock, Texas, nitrate tends to be <45 mg/l, chloride is <20 mg/l, and dissolved solids are <400 mg/l. However, southwest of this line nitrate may exceed 60 mg/l and in some areas exceeds 170 mg/l. Chloride commonly exceeds 500 mg/l and may be >2000 mg/l, and dissolved solids usually exceed 1000 mg/l and may be >8000 mg/l. Regional distribution may be the result of long‐term migration of Ogallala ground water but the present water quality and distribution, as well as time, distance, stratigraphy and permeability, suggest contamination of Ogallala ground water by vertical rather than lateral migration. Most of the high nitrate values (>45 mg/l) occur in areas having sandy soils which have been intensively cultivated, thus leaching of nitrogen‐based fertilizers is suspect. However, the high chloride and dissolved solids, which exist in essentially the same geographic area, probably represent vertical to local lateral seepage of saline water from large alkali lake basins and local vertical migration from saline Cretaceous aquifers.