USGS - NAWQA - Water Quality in South-Central Texas

APPENDIX—WATER-QUALITY DATA FROM SOUTH-CENTRAL TEXAS IN A NATIONAL CONTEXT

For a complete view of South-Central Texas data and for additional information about specific benchmarks used, visit our Web site at http://water.usgs.gov/nawqa/. Also visit the NAWQA Data Warehouse for access to NAWQA data sets at http://infotrek.er.usgs.gov/wdbctx/nawqa/nawqa.home.

This appendix is a summary of chemical concentrations and biological indicators assessed in South-Central Texas. Selected results for this Study Unit are graphically compared to results from as many as 36 NAWQA Study Units investigated from 1991 to 1998 and to national water-quality benchmarks for human health, aquatic life, or fish-eating wildlife. The chemical and biological indicators shown were selected on the basis of frequent detection, detection at concentrations above a national benchmark, or regulatory or scientific importance. The graphs illustrate how conditions associated with each land use sampled in South-Central Texas compare to results from across the Nation and how conditions compare among the several land uses. Graphs for chemicals show only detected concentrations and, thus, care must be taken to evaluate detection frequencies in addition to concentrations when comparing study-unit and national results. For example, simazine concentrations for monitor-well samples of ground water in urban areas were similar to the national distribution, but the detection frequency was much higher (57 percent compared with 18 percent). Graph showing Pesticides in water—Herbicides.

Appendix. Pesticides in water—Insecticides and Volatile organic compounds (VOCs) in ground water.

Appendix. Nutrients in water, Dissolved solids in water and Trace elements in ground water

Appendix. CHEMICALS IN FISH TISSUE AND BED SEDIMENT. Organochlorines in fish tissue (whole body) and bed sediment.

Appendix. Semivolatile organic compounds (SVOCs) in bed sediment. Trace elements in fish tissue (livers) and bed sediment.

Appendix. BIOLOGICAL INDICATORS: Higher national scores suggest habitat disturbance, water-quality degradation, or naturally harsh conditions. The status of algae, invertebrates (insects, worms, and clams), and fish provide a record of water-quality and stream conditions that water-chemistry indicators may not reveal. Algal status focuses on the changes in the percentage of certain algae in response to increasing siltation, and it often correlates with higher nutrient concentrations in some regions. Invertebrate status averages 11 metrics that summarize changes in richness, tolerance, trophic conditions, and dominance associated with water-quality degradation. Fish status sums the scores of four fish metrics (percent tolerant, omnivorous, non-native individuals, and percent individuals with external anomalies) that increase in association with water-quality degradation.

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U.S. Geological Survey Circular 1212

Suggested citation:

Bush, P.W., Ardis, A.F., Fahlquist, Lynne, Ging, P.B., Hornig, C.E., and Lanning-Rush, Jennifer, 2000, Water Quality in South-Central Texas, Texas, 1996–98: U.S. Geological Survey Circular 1212, 32 p., on-line at http://pubs.water.usgs.gov/circ1212/

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