USGS

Water-Level Changes 1977–87, 1987–95, and 1995–2000 in the Chicot and Evangeline Aquifers, Houston-Galveston Region, Texas

By Mark C. Kasmarek and Jennifer Lanning-Rush

Open-File Report 02-377

In cooperation with Harris-Galveston Coastal Subsidence District and the
Fort-Bend Subsidence District


zipped 18 X 22 n. pdf files (9 MB)
8 1/2 X 11 in. pdf files (9,474 KB)

or 8 1/2 X 11 in. jpeg files (613 KB)


Plates

    1. Map showing approximate water-level changes in the Chicot aquifer, Houston-Galveston region, Texas,
        1977–87 (1,650  KB, 18 X 22 in. pdf file)

    2. Map showing approximate water-level changes in the Chicot aquifer, Houston-Galveston region, Texas,
        1987–95 (1,560  KB, 18 X 22 in. pdf file)

    3. Map showing approximate water-level changes in the Chicot aquifer, Houston-Galveston region, Texas,
        1995–2000 (1,884  KB, 18 X 22 in. pdf file)

    4. Map showing approximate water-level changes in the Evangeline aquifer, Houston-Galveston region, Texas,
        1977–87 (1,546  KB, 18 X 22 in. pdf file)

    5. Map showing approximate water-level changes in the Evangeline aquifer, Houston-Galveston region, Texas,
        1987–95 (1,586  KB, 18 X 22 in. pdf file)

    6. Map showing approximate water-level changes in the Evangeline aquifer, Houston-Galveston region, Texas,
        1995–2000 (1,502  KB, 18 X 22 in. pdf file)


INTRODUCTION

This report depicts long-term water-level changes in the Chicot and Evangeline aquifers in the Houston-Galveston region. The Houston-Galveston region comprises Harris, Galveston, Fort Bend, Waller, and Montgomery Counties and adjacent parts of Brazoria, Grimes, Walker, San Jacinto, Liberty, and Chambers Counties. The report was prepared in cooperation with the Harris-Galveston Coastal Subsidence District and the Fort Bend Subsidence District. For the Chicot and Evangeline aquifers, maps show approximate water-level changes for the periods 1977 to 1987 (figs. 1 and 4), 1987 to 1995 (figs. 2 and 5), and 1995 to 2000 (figs. 3 and 6).

Nineteen seventy-seven was the first year that water levels in a network of wells were measured and water-level-altitude maps made for the Chicot and Evangeline aquifers. Nineteen eighty-seven, 1995, and 2000 were years in which land-surface altitudes throughout Harris, Galveston, and Fort Bend Counties were releveled using spirit leveling (1987) and Global Positioning Satellite technology (1995 and 2000); thus the selection of those years for the maps.

The U.S. Geological Survey (USGS) has published annual reports of water-level altitudes and water-level changes for the Chicot and Evangeline aquifers in the Houston-Galveston region since 1979 and separate similar annual reports for the Fort Bend subregion since 1990. Beginning with 2002, the separate annual reports were combined into one report.

GEOHYDROLOGY

The Chicot aquifer (in Holocene- and Pleistocene-age sediments) and the Evangeline aquifer (in Pliocene- and Miocene-age sediments) are the two primary aquifers in the Houston-Galveston region and are part of the Gulf Coast aquifer system. The hydrogeologic units are laterally discontinuous fluvial-deltaic deposits of gravel, sand, silt, and clay that dip and thicken from northwest to southeast. The aquifers crop out in bands inland from and approximately parallel to the coast and become progressively more deeply buried and confined toward the coast. The Chicot outcrop, which comprises the youngest sediments, is the closest of the aquifer outcrops to the coast, followed farther inland by the Evangeline outcrop.

The Chicot aquifer can be differentiated from the geologically similar Evangeline aquifer on the basis of hydraulic conductivity (Carr and others, 1985, p. 10). A weak hydraulic connection between land surface and the Chicot aquifer and between the Chicot and Evangeline aquifers allows vertical movement of water into and between the aquifers; the aquifer system thus is characterized as "leaky" (Gabrysch and Coplin, 1990, p. 2).

The water in the aquifers is fresh (less than 1,000 milligrams per liter dissolved solids concentration) in the region, but becomes more saline in the downdip and deeply buried parts of the aquifers near the coast. In the natural ground-water-flow system, water recharges the aquifers in the unconfined outcrop areas, moves downward and coastward, and discharges vertically as diffuse upward leakage in the confined downdip areas.

WATER-LEVEL MEASUREMENTS

Water-level measurements used as the basis for these change maps were obtained by steel tape, airline, and from reports of well operators. Most wells are pumped once daily, but some are pumped more frequently. Multiple measurements were made when wells were not being pumped; however, antecedent conditions and pumping status of nearby wells were not always known.

REFERENCES

Baker, E.T., Jr., 1979, Stratigraphic and hydrogeologic framework of part of the Coastal Plain of Texas: Texas Department of Water Resources Report 236, 43 p.

Carr, J.E., Meyer, W.R., Sandeen, W.M., and McLane, I.R., 1985, Digital models for simulation of ground-water hydrology of the Chicot and Evangeline aquifers along the Gulf Coast of Texas: Texas Department of Water Resources Report 289, 101 p.

Coplin, L.S., and Santos, H.X., 2000, Water-level altitudes 2000, water-level changes 1977–2000 and 1999–2000, and compaction 1973–99 in the Chicot and Evangeline aquifers, Houston-Galveston region, Texas: U.S. Geological Survey Open-File Report 00–094, 8 sheets.

Gabrysch, R.K., 1979, Approximate altitude of water levels in wells in the Chicot and Evangeline aquifers in the Houston area, Texas, spring 1977 and spring 1978: U.S. Geological Survey Open-File Report 79–334, 4 sheets.

Gabrysch, R.K., and Coplin, L.S., 1990, Land-surface subsidence resulting from ground-water withdrawals in the Houston-Galveston region, Texas, through 1987: Harris-Galveston Coastal Subsidence District Report of Investigations 90–01, 53 p.

Kasmarek, M.C., Coplin, L.S., and Santos, H.X., 1995, Water-level altitudes 1995, water-level changes 1977–95 and 1994–95, and compaction 1973–94 in the Chicot and Evangeline aquifers, Houston-Galveston region, Texas: U.S. Geological Survey Open-File Report 95–182, 8 sheets.

University of Texas, Bureau of Economic Geology, 1968, Geologic atlas of Texas, Beaumont sheet: Austin, scale 1:250,000.

Williams, J.F., III, Lind, W.B., and Coplin, L.S., 1987, Approximate altitude of water levels in wells in the Chicot and Evangeline aquifers in the Houston area, Texas, spring 1987: U.S. Geological Survey Open-File Report 87–233, 2 sheets.



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