In cooperation with the Orange County Commissioner’s Court
Ground-Water Data in Orange County and Adjacent Counties, Texas, 1985–90
By Mark C. Kasmarek
U.S. Geological Survey
Open-File Report 99–603
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Contents
Abstract
Introduction
Purpose and Scope
Acknowledgments
Well-Numbering System
Hydrogeology
Ground-Water Resources
Withdrawals
Water Levels
Altitudes in April 1990
Changes During 1971–90 and 1985–90
Water Quality
Changes in Dissolved Chloride Concentrations
Relation Between Specific Conductance and Dissolved Chloride Concentrations
Summary
Selected References
Glossary
Plates
| 1–5. | Maps showing: | |
| 1. | Locations of selected wells in Orange County and adjacent
counties, Texas (749 KB, 17 X 22) |
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| 2. | Approximate water-level altitudes in wells screened in the lower unit
of the Chicot aquifer in Orange County and adjacent counties, Texas, 1990 (393 KB, 17 X 22) |
|
| 3. | Approximate water-level changes in wells screened in the lower unit of
the Chicot aquifer in Orange County and adjacent counties, Texas, 1971–90 (392 KB, 17 X 22) |
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| 4. | Approximate water-level changes in wells screened in the lower unit of
the Chicot aquifer in Orange County and adjacent counties, Texas, 1985–90 (384 KB, 17 X 22) |
|
| 5. | Distribution of dissolved chloride concentrations in water from wells
screened in the lower unit of the Chicot aquifer in Orange County, Texas,
November–December 1989 (384 KB, 17 X 22) |
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Figures
| 1–2. | Maps showing: | |
| 1. | Location of study area | |
| 2. | Approximate altitude of the base of the Chicot aquifer in Orange County, Texas | |
| 3. | Hydrographs showing changes in water levels in wells screened in the lower unit of the Chicot aquifer in Orange County, Texas | |
| 4. | Conceptual profiles showing (a) relation between freshwater and saline water before pumping begins and (b) development of a saline-water cone during pumping | |
| 5–6. | Maps showing dissolved chloride concentrations in water from selected wells screened in the lower unit of the Chicot aquifer at: | |
| 5. | Site A in southwestern Orange County, Texas, November 1985 | |
| 6. | Site B in southeastern Orange County, Texas, (a) November 1985, (b) October–November 1986, and (c) October 1988 | |
| 7. | Graph showing relation between specific conductance and dissolved chloride concentrations in water from wells screened in the lower unit of the Chicot aquifer, Orange County, Texas, 1985–89 | |
Tables
| 1. | Hydrogeologic correlations for Orange County and adjacent counties, Texas |
| 2. | Average daily rates of ground-water withdrawals for municipal and industrial use from the lower unit of the Chicot aquifer in Orange County, Texas, 1980–89, in million gallons per day |
| 3. | Average daily rates of ground-water withdrawals from the lower unit of the Chicot aquifer at major industrial sites in Orange County, Texas, 1980–89, in million gallons per day |
| 4. | Average daily rates of surface water supplied for municipal and industrial use in Orange County, Texas, 1980–89, in million gallons per day |
| 5. | Average daily rates of ground-water withdrawals from the Evangeline aquifer and lower unit of the Chicot aquifer for public supply in eastern Jefferson, eastern Hardin, and southern Jasper Counties, Texas, 1985–89, in million gallons per day |
| 6. | Water levels in observation wells in Orange County and adjacent counties, Texas, 1985–90 |
| 7. | Records of selected wells in Orange County, Texas, 1985–90 |
| 8. | Chemical analyses of water from selected wells in Orange County, Texas, 1985–90 |
Abstract
The lower unit of the Chicot aquifer is a major source of freshwater for Orange County, Texas. In 1989, the average rate of ground-water withdrawal from the lower unit of the Chicot aquifer in Orange County for municipal and industrial use was 13.8 million gallons per day, a substantial decrease from the historical high of 23.1 million gallons per day in 1972. The average withdrawal for industrial use decreased substantially from 14.4 million gallons per day during 1963–84 to 6.9 million gallons per day during 1985–89. The average withdrawal for municipal use during 1985–89 was 6.8 million gallons per day, similar to the average withdrawal of 5.8 million gallons per day during 1963–84.
Water levels in wells in most of the study area rose during 1985–90. The largest rise in water levels was more than 10 feet in parts of Orange and Pinehurst, north of site B (one of three areas of ground-water withdrawal for industrial use), while the largest decline in water levels was a localized decline of more than 60 feet at site C in south-central Orange County (also an area of withdrawal for industrial use).
Chemical analyses of ground-water samples from the lower Chicot aquifer during 1985–90 indicate that the aquifer contained mostly freshwater (dissolved solids concentrations less than 1,000 milligrams per liter). Dissolved chloride concentrations remained relatively constant in most wells during 1985–90 but could vary greatly between wells within short distances. Saline-water encroachment continued to occur during 1985–89 but at a slower rate than in the 1970s and early 1980s. On the basis of chemical data collected during 1985–89, a relation was determined between specific conductance and dissolved chloride concentration that can be used to estimate dissolved chloride by multiplying the specific conductance by different factors for low or high conductances.
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