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Relation between urbanization and water quality of streams in the Austin area, Texas

Water-Resources Investigations Report 90-4107

Prepared in cooperation with the City of Austin
By:
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Abstract

Selected water-quality properties and constituents of stormflow and base flow were compared to determine the relation between the degree of urbanization and the water quality in a drainage basin. Samples were collected during three flow categories (rising stage and falling stage of stormflow and base flow) at 18 sites on 11 streams. The degree of urbanization is indicated by grouping the sample sites by development based on the percent of impervious cover in the drainage basin. Four development classifications rural, mostly rural, partly urban, and urban were identified based on ranges of impervious cover in the drainage basins. For each site and development classification, the concentrations and densities in samples collected during the rising stage and falling stage of stormflow and during base flow were compared. Samples were collected for physical organics and inorganics, nutrients, indicator bacteria, inorganic trace elements, synthetic organic compounds, and radiochemical constituents.

Except for dissolved solids, the concentrations in samples collected during the rising stage of stormflow were larger than in samples collected during the falling stage. The concentrations in stormflow were larger than in base flow. The concentrations and densities of suspended solids, biochemical oxygen demand, total organic carbon, total nitrogen, total phosphorus, fecal coliforms, and fecal streptococci increased with increased impervious cover.

For the five sample sites that had a sufficient number of samples from each flow category for statistical comparisons, the median concentrations in samples collected during the rising stage and falling stage of stormflow were significantly larger than the base-flow median concentrations. In addition, the concentrations in samples collected during the rising stage were more variable and significantly larger than in those collected during the falling stage of stormflow. Statistical differences between the median concentrations in samples collected during the rising stage and falling stage of stormflow were not evident for the site with the mostly rural drainage basin.

Except for dissolved solids, the median concentrations in samples collected during the rising stage and falling stage of stormflow increased with increasing development classifications. For base flow, the median concentrations were also larger for more urban classifications than for the other classifications.

The ratio of the number of samples with detectable concentrations to the total number of samples analyzed for 18 inorganic trace elements and the concentrations of many of these minor constituents increased with increasing development classifications. Twenty-two of the 42 synthetic organic compounds for which samples were analyzed were detected in one or more samples. The compounds were detected more frequently and in larger concentrations at the sites with more urban classifications.

Study Area

Additional publication details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Relation between urbanization and water quality of streams in the Austin area, Texas
Series title:
Water-Resources Investigations Report
Series number:
90-4107
Year Published:
1990
Language:
English
Publisher:
U.S. Geological Survey
Publisher location:
Austin, TX
Contributing office(s):
Texas Water Science Center
Description:
Document: v, 64 p.; Plate: 24.11 x 33.65 inches
Country:
United States
State:
Texas
City:
Austin
Online Only (Y/N):
N
Additional Online Files (Y/N):
N