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U.S. DEPARTMENT OF THE INTERIORU.S. GEOLOGICAL SURVEY

Base from U.S. Geological Survey Digital data, 1:100,000Universal Transverse Mercator projectionZone 15

IN COOPERATION WITH THEHARRIS-GALVESTON COASTAL SUBSIDENCE DISTRICT

AND FORT BEND SUBSIDENCE DISTRICT

WATER-LEVEL CHANGES 2000–2004 IN THE CHICOT AND EVANGELINE AQUIFERS, HOUSTON-GALVESTON REGION, TEXAS

ByMark C. Kasmarek

2004

OPEN-FILE REPORT 2004–1407Approximate water-level changes, Chicot aquifer, 2000–2004—SHEET 1 OF 2

Kasmarek, M.C., 2004, Water-level changes 2000–2004 in the Chicotand Evangeline aquifers, Houston-Galveston region, Texas

ROSENBERG

RICHMOND

RIVERSIDE

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NAVASOTA MONTGOMERYCONROE

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DAYTON

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BAYTOWN

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JOHNSON SPACE CENTER

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GALVESTON

HOUSTON

Loop 336

Line of equal water-level rise—Intervals 5 and 10 feet

Boundary of study area

EXPLANATION

20

Updip limit of Chicot aquifer (Baker, 1979; Universityof Texas, Bureau of Economic Geology, 1968)

Line of equal water-level decline—Intervals 5 and 10 feet

Line of zero water-level change0

-20

Well in which 2000 and 2004 water levels weremeasured

Figure 1. Map showing approximate water-level changes in the Chicotaquifer, Houston-Galveston region, Texas, 2000–2004.

TEXAS

Study area

REFERENCES

Baker, E.T., Jr., 1979, Strati-graphic 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, Digi-tal models for simulation of ground-water hydrology of the Chicot and Evan-geline 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., and Coplin, L.S., 1990, Land-surface subsi-dence resulting from ground-water withdrawals in the Hous-ton-Galveston region, Texas, through 1987: Harris-Galveston Coastal Subsidence District Report of Investigations 90–01, 53 p.

Kasmarek, M.C., and Lanning-Rush, Jennifer, 2004, Water-levelaltitudes 2004 and water-level changes in the Chicot, Evangeline, and Jasper aquifers and compaction 1973–2003 in the Chicot and Evangeline aquifers, Houston-Galveston region, Texas: U.S. Geological Survey Open-File Report 2004–1084, 13 sheets.

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

INTRODUCTION

This report depicts 2000–2004 water-level changes in the Chicot and Evangeline aquifers in the Houston-Galveston region (figs. 1 and 2). 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.

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 Mio-cene-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 approxi-

mately 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 con-nection between land surface and the Chicot aquifer and between the Chicot and Evangel-

ine 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 fre-quently. Multiple measurements were made when wells were not

being pumped; however, antecedent conditions and pumping sta-tus of nearby wells were not always known.

Note: This change map was generated by contouring the differences between 2000 water-level data (Coplin and

Santos, 2000) and 2004 water-level data (Kasmarek and Lanning-Rush, 2004).

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