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Ground-water withdrawals, water-level changes, land-surface subsidence, and ground-water quality in Fort Bend County, Texas, 1969-87

Water-Resources Investigations Report 90-4012

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Abstract

Fort Bend County, Texas, one of the fastest growing counties in the U.S., is dependent entirely on groundwater for public supply. Withdrawals for public supply increased from 4 Mgal/d (million gallons per day) in 1969 to 28 Mgal/d in 1986. Total withdrawals increased from 56 Mgal/day in 1969 to 72 Mgal/day in 1982, but decreased because of reductions in irrigation withdrawals, to 53 Mgal/d in 1986. The net decline in the potentiometric surfaces from 1969 to 1987 ranged from less than 4 ft in the upper unit and 100 ft in the lower unit of the Chicot aquifer to 125 ft in the Evangeline aquifer. The northeastern part of the county is most susceptible to land-surface subsidence. From 1969-87, chloride concentrations differed by less than 15 mg/L. The median concentrations of dissolved solids were 475 mg/L in the upper unit of the Chicot, 337 mg/L in the lower unit, and 307 mg/L in the Evangeline. Between 1968-69 and 1987, water levels in wells in the upper unit of the Chicot generally fluctuated less than 4 ft and declined in wells in the lower unit of the Chicot from less than 10 ft in most of western Fort Bend County to 100 ft in the northeast. Hydrographs of wells completed in the lower unit of the Chicot showed that water levels continued to decline from 1969 to the early 1980's. The hydrographs of wells located outside of the northeast area generally show a stabilization of water levels after 1982, corresponding to the reductions in withdrawals in the county and neighboring Houston metropolitan area. Withdrawals from the Evangeline aquifer increased from 15% of the total withdrawals in 1969 to 50% in 1986. Water-level declines in wells screened in the Evangeline aquifer during 1969-86 ranged from less than 25 ft in northwestern Fort Bend County to 125 ft in the northeast. In the southwestern one-fourth of the county, decline was less than 50 ft. (USGS)

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Ground-water withdrawals, water-level changes, land-surface subsidence, and ground-water quality in Fort Bend County, Texas, 1969-87
Series title:
Water-Resources Investigations Report
Series number:
90-4012
Edition:
-
Year Published:
1990
Language:
ENGLISH
Publisher:
Dept. of the Interior, U.S. Geological Survey ; Books and Open-File Reports Section [distributor],
Description:
v, 155 p. :ill. ;28 cm.