PLAYA DYNAMICS AND SALINITY: A STUDY OF YELLOW LAKE ON THE HIGH PLAINS OF TEXAS

Saline playas on the Southern High Plains are almost always located on large cattle ranches but they are of limited value to the herds of cattle grazing around their outer margins. Saline playas are often without water for extended periods and, after inundation, they experience considerable evaporative loss leading to hypersaline conditions. The primary goal of this study was to develop a quantitative method that combines the transitory nature of playa lakes and the variability of salinity into a set of parameters that can be used to compare playas or other surface water sources. Regarding water quality, a variable was developed that describes the fraction of observations with salinity levels below the salt tolerance threshold for cattle. With regard to water availability, water depth measurements were used to compute the fraction of time that a playa contains water. These two variables are combined to form a new variable that represents the fraction of time that water is both available and of acceptable quality. To demonstrate the utility of this method, data was collected at Yellow Lake, a large saline playa located on the Yellow House Ranch northwest of Lubbock, Texas. Results suggest that the playa contained water 50.8% of the time over a five-year period but the fraction of water samples with acceptable salinity was only 6.5%. The resulting fraction of time that water was both available and of acceptable quality was only 3.3%. This technique could be used to compare other ephemeral surface water sources in the region.