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-levelaltitude 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.