Geology topics

Research about Dallas, Fort Worth, Texas

Source-linked reports with geographic coverage including Dallas, Fort Worth, Texas.

3 recordsLinked to original sources

USGS1996

Occurrence of polycyclic aromatic hydrocarbons in urban streams as assessed using semipermeable membrane devices, Dallas-Fort Worth metropolitan area, Texas

One of the primary goals of the U.S. Geological Survey's National Water Quality Assessment (NAWQA) Program is to determine the occurrence and distribution of contaminants in stream sediments and tissues of aquatic organisms (Crawford and Luoma, 1993). Metals and persistent organic contaminants are of principal concern. Polycyclic aromatic hydrocarbons (PAHs) are a group of organic compounds that occur abundantly in the environment, are toxic and often carcinogenic to organisms, and could represent a long-term source of contamination. PAHs are metabolized and excreted by most higher vertebrates, particularly fishes, often making assessment of tissues concentrations impossible. Major sources of PAHs are the incomplete combustion of carbonaceous materials and oil spills. The objectives of this fact sheet are to summarize the occurrence of water-borne PAHs in three urban streams in the Dallas- Fort Worth metropolitan area and to assess the use of semipermeable membrane devices (SPMDs) as PAH samplers. One site on each of three streams was selected for monitoring the occurrence of PAHs (fig. 1). The sites were chosen to reflect varied urban land uses and the influences of point- and nonpointsource pollution. The monitoring was done using SPMDs during a 30-day period in late May and June 1994.

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USGS1996

Water-quality assessment of the Trinity River Basin, Texas — Pesticides in streams draining an urban and an agricultural area, 1993-95

Water and bed-sediment samples from streams draining an urban and an agricultural area in the Trinity River Basin, Texas, were analyzed. The samples were collected during March 1993?September 1995 by the Trinity River Basin study-unit team of the National Water-Quality Assessment Program. A comparison of pesticide data for water samples from seven streams in the Dallas-Fort Worth urban area with five streams in an agricultural area in the west-central part of the Trinity River Basin showed detections of 24 herbicides in urban-area streams and 19 herbicides in agricultural-area streams and 10 insecticides in each area. Atrazine, a herbicide, was detected in all samples from both areas. Diazinon, an insecticide, was detected in all samples collected in urban-area streams and in about 60 percent of the samples collected in agricultural-area streams. Concentrations of alachlor, atrazine, fluometuron, metolachlor, and pendimethalin (herbicides) were always greater in agricultural-area streams, and prometon and simazine concentrations were always greater in urban-area streams. Atrazine was the only herbicide with concentrations greater than a health advisory limit of 3 micrograms per liter. Concentrations were greater in about 20 percent of the samples; all were in the agricultural area and occurred during spring and during higher streamflow. Diazinon was the only insecticide with concentrations greater than the health advisory of 0.6 microgram per liter. Concentrations were greater in about 15 percent of the samples from the urban area. All exceedances were during spring through early fall and during all ranges of streamflow. In the agricultural area, atrazine and metolachlor concentrations peaked during spring and early summer and increased with increasing streamflow; in the urban area, carbaryl, chlorpyrifos, and diazinon peaked in April and remained relatively high during the summer and increased with increasing streamflow. A comparison of pesticide data for bed-sediment samples from five urban streams and five agricultural streams showed detections of 11 organochlorine insecticides in the urban area and 1 in the agricultural area. All compounds were either DDT-related or one of the components of chlordane except for mirex and dieldrin.

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USGS1982

Techniques for estimating the magnitude and frequency of floods in the Dallas - Fort Worth metropolitan area, Texas

Equations for predicting the magnitude and frequency of floods in the Dallas-Fort Worth metropolitan area were developed from recorded data from streams with drainage areas ranging in size from 1.25 to 66.4 square miles. The U. S. Geological Survey urban rainfall-runoff model was used to generate long-term flood-discharge record for gaged streams in the area. Simulated and recorded annual-peak data were subjected independently to log Pearson III frequency analyses. The results were weighted to determine appropriate discharges for selected 2-, 5-, 10-, 25-, 50-, and 100-year recurrence intervals. These T-year values were then used as the dependent variables in a multiple regression analysis. The independent variable determined to be statistically significant and retained in the resulting equations were drainage area and an urbanization index that expresses the degree of urban development. Analysis of the results shows that a land-use change from rural to fully urbanized is accompanied by a 180% increase in discharge of a flood with a 5-year recurrence interval and about 100% increase in discharge of a flood with a 100-year recurrence interval.

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