Scientific Investigations Map 3138
Most of the subsidence in the Houston-Galveston region has occurred as a direct result of groundwater withdrawals for municipal supply, industrial use, and irrigation that depressured and dewatered the Chicot and Evangeline aquifers causing compaction of the clay layers of the aquifer sediments. This report, prepared by the U.S. Geological Survey, in cooperation with the Harris-Galveston Subsidence District, City of Houston, Fort Bend Subsidence District, and Lone Star Groundwater Conservation District, is one in an annual series of reports depicting water-level altitudes and water-level changes in the Chicot, Evangeline, and Jasper aquifers and compaction in the Chicot and Evangeline aquifers in the Houston-Galveston region. The report contains maps showing 2010 water-level altitudes for the Chicot, Evangeline, and Jasper aquifers, respectively; maps showing 1-year (2009–10) water-level-altitude changes for each aquifer; maps showing 5-year (2005–10) water-level-altitude changes for each aquifer; maps showing long-term (1990–2010 and 1977–2010) water-level-altitude changes for the Chicot and Evangeline aquifers; a map showing long-term (2000–10) water-level-altitude change for the Jasper aquifer; a map showing locations of borehole extensometer sites; and graphs showing measured compaction of subsurface material at the extensometers from 1973, or later, through 2009. Tables listing the data used to construct each aquifer-data map and the compaction graphs are included.
Water levels in the Chicot, Evangeline, and Jasper aquifers were measured during December 2009–March 2010. In 2010, water-level-altitude contours for the Chicot aquifer ranged from 200 feet below National Geodetic Vertical Datum of 1929 or North American Vertical Datum of 1988 (hereinafter, datum) in a small area in southwestern Harris County to 200 feet above datum in central to southwestern Montgomery County. Water-level-altitude changes in the Chicot aquifer ranged from a 49-foot decline to a 67-foot rise (2009–10), from a 25-foot decline to a 35-foot rise (2005–10), from a 40-foot decline to an 80-foot rise (1990–2010), and from a 140-foot decline to a 200-foot rise (1977–2010). In 2010, water-level-altitude contours for the Evangeline aquifer ranged from 300 feet below datum in north-central Harris County to 200 feet above datum at the boundary of Waller, Montgomery, and Grimes Counties. Water-level-altitude changes in the Evangeline aquifer ranged from a 58-foot decline to a 69-foot rise (2009–10), from an 80-foot decline to an 80-foot rise (2005–10), from a 200-foot decline to a 220-foot rise (1990–2010), and from a 320-foot decline to a 220-foot rise (1977–2010). In 2010, water-level-altitude contours for the Jasper aquifer ranged from 200 feet below datum in south-central Montgomery County to 250 feet above datum in eastern-central Grimes County. Water-level-altitude changes in the Jasper aquifer ranged from a 39-foot decline to a 39-foot rise (2009–10), from a 110-foot decline to no change (2005–10), and from a 180-foot decline to no change (2000–10).
Compaction of subsurface materials (mostly in the clay layers) composing the Chicot and Evangeline aquifers was recorded continuously at 13 borehole extensometers at 11 sites. For the period of record beginning in 1973, or later, and ending in December 2009, cumulative clay compaction data measured by 12 extensometers ranged from 0.088 foot at the Texas City-Moses Lake site to 3.559 foot at the Addicks site. The rate of compaction varies from site to site because of differences in groundwater withdrawals near each site and differences among sites in the clay-to-sand ratio in the subsurface materials. Therefore, it is not possible to extrapolate or infer a rate of clay compaction for an area based on the rate of compaction measured at a nearby extensometer.
Revised March 15, 2011
First posted December 22, 2010
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Kasmarek, M.C., Johnson, M.R., and Ramage, J.K., 2010, Water-level altitudes 2010 and water-level changes in the Chicot, Evangeline, and Jasper aquifers and compaction 1973–2009 in the Chicot and Evangeline aquifers, Houston-Galveston region, Texas: U.S. Geological Survey Scientific Investigations Map 3138, 17 p., 16 sheets, 1 appendix.
Data Collection and Analysis Methods
Water-Level Altitudes and Changes
Compaction in the Chicot and Evangeline Aquifers
Appendix 1—Well Location Maps