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Relation of water chemistry of the Edwards aquifer to hydrogeology and land use, San Antonio Region, Texas

Water-Resources Investigations Report 87-4116

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Abstract

Water-chemistry data from the Edwards aquifer, Texas, for 1976-85, consisting of nearly 1,500 chemical analyses from 280 wells and 3 springs, were used to statistically evaluate relations among groundwater chemistry, hydrogeology, and land use. Five land uses associated with sampled wells were classified from published information and field surveys. Four major subareas of the aquifer were defined to reflect relative susceptibility of groundwater to contaminated originating from human activities using hydrogeologic and tritium data. Water from an agricultural area over the unconfined zone had the greatest median concentration of nitrite plus nitrate. Larger nitrite plus nitrate concentrations were spatially associated with large tritium concentrations and nitrogen isotopic ratios characteristic of streamflow recharge. Detections of fecal coliform bacteria were associated mainly with water from wells completed in the unconfined zone. Most occurrences of tetrachloroethylene, 1,2-(trans)-dichloroethylene, trichlorofluoromethane, 1,1,1-trichloroethane, and 2,4-D in water were associated with wells completed in the unconfined zone of the aquifer. The percentage of samples in which arsenic, barium, lead, and zinc were detected was similar among subareas; the samples were from the freshwater parts of the aquifer. Large lead and zinc concentrations were associated with sampling pumpage less than 1,000 gallons. (USGS)

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Relation of water chemistry of the Edwards aquifer to hydrogeology and land use, San Antonio Region, Texas
Series title:
Water-Resources Investigations Report
Series number:
87-4116
Edition:
-
Year Published:
1987
Language:
ENGLISH
Publisher:
U.S. Geological Survey,
Description:
vi, 100 p. :ill., maps ;28 cm.