Status of groundwater-level altitudes and long-term groundwater-level changes in the Chicot, Evangeline, and Jasper aquifers, Houston-Galveston region, Texas, 2020

Abstract

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Treatment of the Chicot and Evangeline aquifers as a single hydrogeologic unit and use of geostatistical interpolation methods to develop gridded surfaces of water-level altitudes and water-level changes in the Chicot and Evangeline aquifers (undifferentiated) and Jasper aquifer, greater Houston area, Texas, 2021

“…The following overview of the geology and hydrogeology of the study area is modified from Kasmarek and Ramage (2017) and Braun and Ramage (2020). The Gulf Coast aquifer system hydrogeologic units include the Chicot aquifer, the Evangeline aquifer, the Burkeville confining unit, the Jasper aquifer, and the Catahoula confining unit (figs.…”

“…Because of this hydraulic connection, water-level changes (changes in the depth to water in feet below land surface) that occur in one aquifer can affect water levels in the adjoining aquifer (Kasmarek and others, 2010). Supporting evidence of the interaction of groundwater flow between the Chicot and Evangeline aquifers includes maps of long-term water-level changes that show areas where rises and declines are approximately spatially coincident and colocated wells with different screened-interval depths where rises or declines in water levels are approximately coincident in time (for example, Braun and others, 2019;Braun and Ramage, 2020). Additional evidence of the hydraulic connection between the Chicot and Evangeline aquifers is provided by Borrok and Broussard (2016, p. 330); their geochemical evaluation of the Chicot aquifer system from 1993 to 2015 in Louisiana indicated that in some years (1998, 2008, and 2011) certain wells screened in the Chicot aquifer "appeared to be tapping water with a geochemistry (temperature, salinity, alkalinity, [and so forth]) matching the underlying Evangeline aquifer."…”

“…In 2004, as additional wells with reliable water-level data were inventoried, revised water-level-altitude maps for the Jasper aquifer were prepared (Kasmarek and Lanning-Rush, 2004;Kasmarek and others, 2006;Kasmarek and Houston, 2007). Since 2007, comprehensive maps for the Jasper aquifer have been included in the annual series of water-level reports for the greater Houston area (Kasmarek and Houston, 2008;Kasmarek and others, 2009Kasmarek and others, , 2010Kasmarek and others, , 2012Kasmarek and others, , 2013Kasmarek and others, , 2014Kasmarek and others, , 2015Kasmarek and others, , 2016Johnson and others, 2011;Kasmarek and Ramage, 2017;Shah and others, 2018;Braun and others, 2019;Braun and Ramage, 2020).…”

“…This report, prepared by the USGS in cooperation with the HGSD, City of Houston, FBSD, LSGCD, and BCGCD, describes two substantial updates to the ways in which water-level altitudes and water-level changes in the greater Houston area are presented relative to previous USGS reports (for example, Kasmarek and Houston, 2008;Kasmarek and others, 2009Kasmarek and others, , 2010Kasmarek and others, , 2012Kasmarek and others, , 2013Kasmarek and others, , 2014Kasmarek and others, , 2015Kasmarek and others, , 2016Johnson and others, 2011;Kasmarek and Ramage, 2017;Shah and others, 2018;Braun and others, 2019;Braun and Ramage, 2020). The Chicot and Evangeline aquifers have traditionally been depicted as separate aquifers (figs.…”

“…The second update concerns the methods used to depict water-level altitudes and water-level changes in the greater Houston area in interpretive reports. Instead of the manual contouring methods that have historically been used in the annual USGS interpretive report series (for example, Braun and others, 2019;Braun and Ramage, 2020), geostatistical interpolation methods are used to develop gridded surfaces of water-level altitudes and water-level changes starting with the 2021 annual report . As part of the second update, the areal extent of the gridded surfaces is refined through the use of a masking process.…”