Direct measurement of infiltration through a playa wetland using automated double ring infiltrometers



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Playa lakes are circular formations that appear as indentions in the earth’s surface and are thought to be of high importance to recharging the aquifer beneath the Southern High Plains. This thesis examines the relationship between the volume of water and the infiltration rate of playa lakes to the recharge of the Ogallala Aquifer. Four sets of double ring infiltrometers were installed in the basin of a cropland playa to directly measure the infiltration rate of a ponded playa. A cropland playa is playa surrounded mostly, if not totally, by arable land. The playa located in Lubbock County on the Southern High Plains was selected to be mapped using high resolution global positioning system to quantify area and volume. Due to differences in watershed management around the playa and modifications to upland soils resulting in uneven sedimentation across the playa basin, the rings were unable to be evenly spaced. The sets of double ring infiltrometers were placed in relatively close proximity on a level surface near the deepest part of the basin. The infiltrometers were spaced far enough away from each other that they would not affect one another’s infiltration data. A two meter core was taken from three predetermined locations to become the center of the inner rings and a two meter thermistor probe reinserted in the openings. Upon completion of installing the double ring infiltrometers, the rings were rapidly filled to a twenty centimeter hydraulic head and held at the constant depth for three days to simulate a flooding and ponding event. Using a high resolution flow meter and a data logger capable of counting high frequency pulses, the amount of water applied over time was recorded and analyzed. The methods and results of the field trial pertaining to the double ring infiltration are described in detail. The results were used to calculate the amount of infiltration through a typical playa basin, which equates to approximately 0.010 cm min-1 for the double ring infiltrometers and 0.058 cm min-1 for the single ring infiltrometers. The data from this thesis validates the hypothesis that a steady-state infiltration rate is more achievable when using a double ring infiltrometer versus a single ring infiltrometer.



Infiltration, Infiltrometer