Spatiotemporal Variations in West Texas Playa Wetlands Mapped from Sentinel-2

The improved spatial, spectral, and temporal resolution of Sentinel-2 satellite imagery compared to widely used Landsat imagery allows for many small, variable bodies of water such as intermittent rivers, glacial lakes, rice paddies, and ephemeral wetlands to be studied in depth for the first time.  Across the Texas High Plains, USA, playa lakes are highly sensitive to wet/dry cycles, and are noted for their critical ecological importance in the region, providing habitat for many species of birds and other animals. The playas are also known to be important features for aquifer recharge in some areas. While sporadic aircraft studies and satellite evaluations of the larger playas in the region have been conducted previously from Landsat, no known study has utilized the improved capabilities of Sentinel-2 imagery to document the numerous smaller playas in the region. In this study, we analyze playa lakes across northwestern Texas, USA between 2016-2020  using high-resolution spectral satellite imagery from the European Space Agency’s Sentinel-2 mission. The Semi-Automatic Classification plugin for QGIS is used to document spatial and temporal changes in the areal extent of water in seasonal playa lakes in the High Plains region of Texas. Several case studies of the spatial and temporal evolution of the playa lakes from Sentinel-2 imagery will be presented, as well as applications for seasonal ecological monitoring and groundwater recharge monitoring.   Images taken of the same playa lakes at different times are compared to determine the rate at which the amount of water is changing. Using data from the nearest available weather stations, the amount of water loss due to evaporation is estimated. This is compared to the observed water loss to estimate the amount of water percolating into the ground where it may be contributing to aquifer recharge. This study aims to be a proof of concept for a method for operationally monitoring the state of playa lakes across the region for ecological applications, as well as to quantify potential groundwater recharge.