Evapotranspiration Measured at two Rangeland sites in Victoria County, South-Central Texas, 2015-2018

The U.S. Geological Survey and Desert Research Institute, in cooperation with the Natural Resources Conservation Service, Texas State Soil and Water Conservation Board, Victoria County Groundwater Conservation District, Victoria Soil and Water Conservation District, and the San Antonio River Authority, evaluated the hydrologic effects of Vachellia farnesiana var. farnesiana (huisache) removal on rangeland evapotranspiration in Victoria County, Texas. Measurements of evapotranspiration (ET), rainfall, and related properties were made at two sites during March 2015 through August 2018. One site was predominately grassland. The other site was dominated by dense huisache vegetation that was removed about halfway through the study period. To obtain the meteorological and surface energy flux data needed for the calculation of ET, the two sites were instrumented with LI-COR Biosciences eddy-covariance systems (LI-COR Biosciences, 2019). The resulting ET data were examined for differences between the locations and differences between the pre-removal (2015-16) and post-removal (2017-18) periods to assess the effects of huisache removal on ET. ET measurements were made using the eddy-covariance method and were supplemented by remote-sensing estimates of ET derived from thermal and optical satellite images. The data presented in this data release include various types of meteorological data (for example air temperature, relative humidity, wind speed and direction, and precipitation) and various energy flux data pertaining to ET (for example latent and sensible heat flux). Turbulent fluxes were compared to measured radiative fluxes to assess the energy budget. The sensible-heat flux was computed by taking variations in temperature into consideration. The relation between a given ET rate and the associated latent-heat flux was calculated. Details of the various energy flux calculation are described in the LI-COR Biosciences, 2016. The methods are further described along with the results of the study in the companion report (U.S. Geological Survey Scientific Investigations report 2020-5008).