Playa dynamics and salinity: A study of Yellow Lake on the High Plains of Texas

Authors: Stout, John

Submitted to: Texas Journal of Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2022
Publication Date: 12/30/2022
Citation: Stout, J.E. 2022. Playa dynamics and salinity: A study of Yellow Lake on the High Plains of Texas. Texas Journal of Science. 74(1): Article 6. https://doi.org/10.32011/txjsci_74_1_Article6.
DOI: https://doi.org/10.32011/txjsci_74_1_Article6

Interpretive Summary: In the semi-arid Southern High Plains, securing an adequate supply of freshwater can be a challenge and will likely become more challenging in the future as groundwater resources are gradually depleted. In a region with limited water resources, one must consider all available sources including those considered to be of limited value. For a source of water to be of value it must provide a dependable supply and the available water must be of sufficient quality such that it does not cause adverse health effects. Saline playa lakes often fall short with regard to both of these criteria. Although saline playas provide critical habitat for roosting sandhill cranes, shorebirds, and other migrating waterfowl, they are of little value to the herds of cattle grazing around their outer margins. Saline playas are often dry for extended periods and they experience considerable evaporative water loss leading to significant increases in salinity. The primary goal of this study was to develop a quantitative method that could combine the transitory nature of playa lakes and the variability of salinity into a set of parameters that could be used to compare and contrast playas or other surface water sources. Regarding water quality, a variable was developed that describes the fraction of samples with salinity levels below the salt tolerance threshold for cattle. With regard to water availability, a continuous series of water depth measurements were used to compute the fraction of time that a playa contains water. Since a water sample can only be obtained when water is available, these two variables can be combined to form a new variable that represents the fraction of time that water is both available and of acceptable water 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 49.7% of the time over the five-year sampling period but the fraction of samples with salinity levels below the salt tolerance threshold for cattle was only 6.7%. The resulting fraction of time that water was both available and of acceptable water quality was only 3.3%. Clearly, Yellow Lake is not a reliable source of drinking water for cattle. However, this same technique could be applied to other playas in the region to determine if any of these shallow lakes are more suitable for watering cattle.

Technical Abstract: There are fifty saline playas scattered across the Southern High Plains of North America. Almost all are located on cattle ranches but they are of little value to cattle grazing around their outer margins. Saline playas are often without water for extended periods and they experience considerable evaporative water loss leading to significant increases in salinity. The primary goal of this study was to develop a quantitative method that could combine the transitory nature of playa lakes and the variability of salinity into a set of parameters that could be used to compare playas or other surface water sources. Regarding water quality, a variable was developed that describes the fraction of samples with salinity levels below the salt tolerance threshold for cattle. With regard to water availability, a continuous series of water depth measurements were used to compute the fraction of time that a playa contains water. Since a water sample can only be obtained when water is available, these two variables can be combined to form a new variable that represents the fraction of time that water is both available and of acceptable water 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 49.7% of the time over the five-year sampling period but the fraction of samples with salinity levels below the salt tolerance threshold for cattle was only 6.7%. The resulting fraction of time that water was both available and of acceptable water quality was only 3.3%. This same technique could be applied to other playas in the region to determine if any of these shallow lakes are more suitable for watering cattle.