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Research about Texas

Source-linked reports with geographic coverage including Texas.

At least 757 records · Page 42Linked to original sources
USGS1997

Distribution and community structure of ichthyoplankton in Laguna Madre seagrass meadows: Potential impact of seagrass species change

Seasonal ichthyoplankton surveys were made in the lower Laguna Madre, Texas, to compare the relative utilization of various nursery habitats (shoal grass, Halodule wrightii ; manatee grass, Syringodium filiforme ; and unvegetated sand bottom) for both estuarine and offshore-spawned larvae. The species composition and abundance of fish larvae were determined for each habitat type at six locations in the bay. Pushnet ichthyoplankton sampling resulted in 296 total collections, yielding 107,463 fishes representing 55 species in 24 families. A broad spectrum of both the biotic and physical habitat parameters were examined to link the dispersion and distribution of both pre-settlement and postsettlement larvae to the utilization of shallow seagrass habitats. Sample sites were grouped by cluster analysis (Ward’s minimum variance method) according to the similarity of their fish assemblages and subsequently examined with a multiple discriminant function analysis to identify important environmental variables. Abiotic environmental factors were most influential in defining groups for samples dominated by early larvae, whereas measures of seagrass complexity defined groups dominated by older larvae and juveniles. Juvenile-stage individuals showed clear habitat preference, with the more shallow Halodule wrightii being the habitat of choice, whereas early larvae of most species were widely distributed over all habitats. As a result of the recent shift of dominance from Halodule wrightii to Syringodium filiforme , overall reductions in the quality of nursery habitat for fishes in the lower Laguna Madre are projected.

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USGS1997

Effects of climate change on southeastern forests

Forests of the coastal plain region of the southeastern United States are among the most productive in North America. Because they form the basis of a large timber and wood products industry, these forests are of considerable economic importance. Also, the forests are rich in plant and animal species. Because they are diverse as well as productive, they have considerable conservation importance. Therefore, understanding potential impacts of climate change on southern forests is critical.

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USGS1997

Discharge measurement in tidally affected channels during a hydrographic estuarine survey of Sabine Lake, Texas

A hydrographic survey of Sabine Lake, a broad, shallow estuary lying on the Texas-Louisiana border, was conducted in June 1996 to help address questions relating to potential environmental effects of future water demands in Texas. The use of a variety of new instruments in this study is one means by which automation is improving efficiency and effectiveness of these efforts by increasing the quality and quantity of data collected.

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USGS1997

Summary of surface-water hydrologic data for the Houston metropolitan area, Texas, water years 1964-89

The study area, a metropolitan area in southeast Texas about 45 miles north of the Gulf of Mexico, has been undergoing extensive urban development since the 1950s. The Houston Urban Runoff Program was begun by the U.S. Geological Survey in water year 1964 to define the magnitude and frequency of flood peaks, to determine the impact of continuing urban development on surface-water hydrologic responses, and to determine variations in stream water quality for different flow conditions, seasons, and urban development. An extensive data base has been developed. During water years 1964-89, the Houston Urban Runoff Program collected information from a total of 54 U.S. Geological Survey streamflow-gaging stations, 30 U.S. Geological Survey water-quality sampling sites, and 102 rain gages (operated by the U.S. Geological Survey, the National Weather Service, and local agencies). In addition, basin characteristics were developed to aid in understanding the effects of urban development on surface-water hydrologic responses. Surface-water hydrologic data on diskettes describe the 54 U.S. Geological Survey streamflow-gaging stations, list annual peaks (and where available, peaks above an arbitrary base) for 50 streamflow sites, tabulate 1,125 storm hydrographs from 43 sites, and document 102 waterquality parameters determined from 3,242 available samples.

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USGS1997

Water-level altitudes in wells completed in the Chicot and Evangeline aquifers, Fort Bend County and adjacent areas, Texas, January-February 1992, 1993, and 1994

This report depicts annual water-level altitudes for 3 consecutive years in the Chicot and Evangeline aquifers in Fort Bend County and adjacent areas, Texas. The report, prepared in cooperation with the Fort Bend Subsidence District, presents maps for the Chicot and Evangeline aquifers showing the approximate water-level altitudes in wells in 1992 and 1994. The most recent previously published water-level-altitude maps (and water-level-change maps) for the two aquifers are by Coplin and others (1197). The earliest water-level-altitude maps (and water-level-change maps) for the Chicot aquifer are by Wesselman (1972). The first maps of water-level altitudes (and water-level changes) for the Chicot and Evangeline aquifers are by Locke (1990).

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USGS1997

Water-level altitudes in wells completed in the Chicot and Evangeline aquifers, Houston-Galveston region, Texas, January-February 1992, 1993, and 1994

This report depicts annual water-level altitudes for 3 consecutive years in the Chicot and Evangeline aquifers in the Houston-Galveston region, Texas. The report, prepared in cooperation with the city of Houston and the Harris-Galveston Coastal Subsidence District, presents maps for the Chicot and Evangeline aquifers showing the approximate water-level altitudes in wells in 1992 and 1994. The most recent previously published water-level-altitude maps (and water-level-change maps) for the two aquifers in the region are by Kasmarek and others (1997). The Houston-Galveston region includes Harris and Galveston Counties and adjacent parts of Brazoria, Fort Bend, Waller, Montgomery, Liberty, and Chambers Counties.

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USGS1997

Hydrogeology and ground-water flow in the Edwards-Trinity aquifer-system, west-central, Texas

Two finite-element ground-water flow models were developed for the Edwards–Trinity aquifer system, west-central Texas, to gain a better understanding of the flow system; one ground-water flow model was developed at a large scale to simulate the regional system and contiguous, hydraulically connected units, and one model was constructed at a smaller more detailed scale to simulate the most active areas of the system. The study area is divided into four geographic subareas: the Trans-Pecos (9,750 square miles), the Edwards Plateau (23,750 square miles), the Hill Country (5,500 square miles), and the Balcones fault zone (3,000 square miles). The major aquifers within the study area are the Edwards–Trinity aquifer underlying the Trans-Pecos and Edwards Plateau, the Trinity aquifer underlying the Hill Country, and the Edwards aquifer in the Balcones fault zone. Hydraulically connected aquifers include the High Plains aquifer north of the Edwards Plateau, and the Cenozoic Pecos alluvium aquifer adjacent to both the Trans-Pecos and the Edwards Plateau along the Pecos River. Minor contiguous aquifers include the Dockum, Ellenburger– San Saba, Marble Falls, Hickory, and Lipan, which is adjacent to the Colorado River in Tom Green and Concho Counties, Texas. The ground-water flow equations solved by the finite-element method are based on conservation of mass and energy. The equation for ground-water flow assumes laminar flow through a porous media. In places, the Edwards–Trinity aquifer system is a fractured karst system in which ground water flows through caverns and other features of secondary porosity development. The regional and subregional models were constructed to synthesize the known hydrologic boundaries and geologic structures into a heterogeneous continuum model of the karst ground-water flow system, rather than simulate the flow through specific fractures and caverns. A heterogeneous continuum or equivalent porous media approach uses an effective transmissivity and anisotropy for each element of the models. The models are calibrated both on water levels (representing potential energy) and estimates of recharge and discharge (for a realistic mass balance). A two-dimensional one-layer large-scale model (55,600 square miles) was developed for the Edwards–Trinity aquifer system and contiguous, hydraulically connected units, in westcentral Texas. A quasi-three-dimensional, multilayer more detailed scale ground-water flow model (12,300 square miles) was applied to the major aquifers of the Edwards–Trinity aquifer system in the Hill Country and the Balcones fault zone, and in part of the Edwards Plateau. The ground-water flow system in most of the study area within the Trans-Pecos and Edwards Plateau can be approximated with a one-layer regional model under steady-state conditions. Regionally, the Edwards–Trinity aquifer system in the Trans-Pecos and Edwards Plateau has been relatively static. Potentiometric maps from predevelopment and postdevelopment (winter 1974–75) indicate small differences in water levels. In local areas in the Trans-Pecos (in Pecos and Reeves Counties), ground-water withdrawals have exceeded recharge resulting in more than 300 feet of drawdown. Measurable differences between the 1974 and predevelopment potentiometric surfaces have been observed in small areas in the Trans-Pecos and in the northwestern part of the Edwards Plateau. The largest water-level declines in the Trans-Pecos have been observed in Pecos and Reeves Counties, and declines greater than 300 feet have been measured in Reeves County. Comparison of pre- and postdevelopment water budgets for the regional model indicates that the increase in groundwater withdrawals has captured 20 percent of the water that would have naturally discharged to streams, and 30 percent of the natural discharge to springs after ground-water development. Induced recharge from streams to the ground-water system increased by 12 percent in the postdevelopment simulation compared to the predevelopment simulation.

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USGS1997

Water-quality assessment of the Rio Grande Valley, Colorado, New Mexico and Texas: Ground-water quality in the Rio Grande flood plain, Cochiti Lake, New Mexico, to El Paso, Texas, 1995

From March to May of 1995, water samples were collected from 30 wells located in the flood plain of the Rio Grande between Cochiti Lake, New Mexico, and El Paso, Texas. These samples were analyzed for a broad host of constituents, including field parameters, major constituents, nutrients, dissolved organic carbon, trace elements, radiochemicals, pesticides, and volatile organic compounds. The main purpose of this study was to observe the quality of ground water in this part of the Rio Grande Valley study unit of the U.S. Geological Survey National Water-Quality Assessment program. The sampling effort was limited to the basin- fill aquifer beneath the above-defined reach of the Rio Grande flood plain because of the relative homogeneity of the hydrogeology, the large amount of ground-water use for public supply, and the potential for land-use activities to affect the quality of ground water. Most of the wells sampled for the study are used for domestic purposes, including drinking water. Depths to the tops of the sampling intervals in the 30 wells ranged from 10 to 345 feet below land surface, and the median was 161.5 feet; the sampling intervals in most of the wells spanned about 10 feet or less. Quality-control data were collected at three of the wells. A significant amount of variation was found in the chemical composition of ground water sampled throughout the study area, but the water generally was found to be of suitable chemical quality for use as drinking water, according to current enforceable standards established by the U.S. Environmental Protection Agency (EPA). Nutrients generally were measured at concentrations near or below their method reporting limits. The most dominant nutrient species was nitrite plus nitrate, at a maximum concentration of 1.9 milligrams per liter (as N). Only eight of the trace elements analyzed for had median concentrations greater than their respective minimum reporting levels. Water from one well exceeded the lifetime health advisory established by the EPA for molybdenum; water from a different well exceeded the proposed EPA maximum contaminant level for uranium. Gross alpha and gross beta particle activities generally appeared to strongly correlate with quantities of uranium and potassium, respectively, detected in ground water. However, water from one well exceeded the EPA maximum contaminant level for gross alpha particle activity and may exceed the EPA maximum contaminant level for beta particle and photon activity, although current data on gross beta particle activities are not conclusive on this point. Radon concentrations did not appear to directly correlate with uranium concentrations. The herbicide prometon was the only synthetic organic compound detected in ground water in the study area, and was detected in only one well, at a concentration of 0.038 microgram per liter. This well is shallow and is not used for drinking water. With the exception of the one detection of prometon, no strong evidence was found of effects on ground-water quality from human activities. Therefore, most of the water sampled probably recharged at the margins of the alluvial basins or recharged through the flood plain before human development began. With respect to major constituents, the concentrations of dissolved solids ranged from 209 to 3,380 milligrams per liter, and the median concentration was 409.5 milligrams per liter. There is evidence that the overall chemical composition of ground water in the study area may be affected by several processes, including cation exchange, feldspar weathering, calcite dissolution and precipitation, dissolution of volcanic glass, and microbial activity. Several chemical constituents in ground water showed relatively distinct spatial patterns that appear to be related to one or more of these processes.

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USGS1997

Regional equations for estimation of peak-streamflow frequency for natural basins in Texas

Peak-streamflow frequency estimates are needed for flood-plain management; for objective assessment of flood risk; and for cost-effective design of dams, levees, other flood-control structures, roads, bridges, and culverts. Peak-streamflow frequency represents the peak discharges for recurrence intervals of 2, 5, 10, 25, 50, and 100 years. The U.S. Geological Survey, in cooperation with the Texas Department of Transportation, conducted an investigation to develop regional regression equations for the estimation of peak-streamflow frequency for ungaged sites in natural basins in Texas. Peak-streamflow frequency data from streamflow-gaging stations in natural drainage basins of Texas were used. Peak-streamflow frequency for 559 Texas stations with natural (unregulated and rural or nonurbanized) basins was estimated with annual peak-streamflow data through 1993. The peak-streamflow frequency and drainage-basin characteristics for the Texas stations were used to develop 16 sets of equations to estimate peak-streamflow frequency for ungaged natural stream sites in each of 11 regions in Texas. The relation between peak-streamflow frequency and contributing drainage area for 5 of the 11 regions is curvilinear, requiring that one set of equations be developed for drainage areas less than 32 square miles and another set be developed for drainage areas greater than 32 square miles. These equations, developed through multiple-regression analysis using weighted least squares, are based on the relation between peak-streamflow frequency and basin characteristics for streamflow-gaging stations. The regions represent areas with similar flood characteristics. The use and limitations of the regression equations also are discussed. Additionally, procedures are presented to compute the 50-, 67-, and 90-percent confidence limits for any estimation from the equations. Also, supplemental peak-streamflow frequency and basin characteristics for 105 selected stations bordering Texas are included in the report. This supplemental information will aid in interpretation of flood characteristics for sites near the state borders of Texas.

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USGS1997

Water-quality assessment of south-central Texas: Occurrence and distribution of volatile organic compounds in surface water and ground water, 1983-94, and implications for future monitoring

The study area of the South-Central Texas study unit of the National Water-Quality Assessment Program comprises the Edwards aquifer in the San Antonio region and its catchment area. The first phase of the assessment includes evaluation of existing water-quality data for surface water and ground water, including volatile organic compounds, to determine the scope of planned monitoring. Most analyses of volatile organic compounds in surface water are from the National Pollutant Discharge Elimination System sites in San Antonio, Texas. Nine volatile organic compounds were detected at the six sites. The three compounds with the most detections at National Pollutant Discharge Elimination System sites are 1,2,4-trimethylbenzene, toluene, and xylene. Analysis of volatile organic compounds in ground water was limited to Edwards aquifer wells. Twenty-eight volatile organic compounds were detected in samples from 89 wells. The five most commonly detected compounds in samples from wells, in descending order, are tetrachloroethene, trichloroethene, bromoform, chloroform, and dibromochloromethane. Detections of volatile organic compounds in surface water and ground water within the South-Central Texas study area are limited to site-specific sources associated with development; therefore, planned monitoring for possible detections of volatile organic compounds as part of the National Water-Quality Assessment Program will emphasize areas of expanding population and development. Monitoring of volatile organic compounds is planned at National Pollutant Discharge Elimination System sites, at basic fixed surface-water sites, and in the ground-water study-unit surveys.

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USGS1997

Integrity of production wells and confining unit at the Naval Weapons Industrial Reserve Plant, Dallas, Texas, 1995

Ground water in the shallow alluvial aquifer is contaminated at the Naval Weapons Industrial Reserve Plant, Dallas, Texas. Five production wells at the site are cased through the alluvial aquifer and underlying units and are screened in either the Paluxy or Twin Mountains aquifers. Three abandoned wells, originally completed in the Twin Mountains aquifer but filled with drilling mud in 1958, also penetrate the alluvial aquifer. The Paluxy and Twin Mountains aquifers are used for drinking-water supplies in and around the Dallas-Fort Worth metroplex. Trichloroethylene and its degradation products, dichloroethylene and vinyl chloride, and the metal chromium previously have been detected in the shallow alluvial aquifer. Current (1995) analyses of water-quality samples taken from the static water column of the five production wells and one of the abandoned wells indicate no trichloroethylene, dichloroethylene, or vinyl chloride in the water column of these wells. Chromium was detected in all samples, but concentrations were less than the practical quantitation limit, which is the regulatory action level for this site. The results of borehole geophysical log analysis indicate that two of the production wells could have vertically connected intervals where cement bonding in the well annulus is poor. The other production wells have overall good bonding. Temperature logs do not indicate flow behind casing except in the screened interval of one well. Geophysical logs show the Eagle Ford Shale ranges from 147 to 185 feet thick at the site. The Eagle Ford Shale has low permeability and a high plasticity index. These physical characteristics make the Eagle Ford Shale an excellent confining unit.

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USGS1997

Light attenuation in a shallow, turbid reservoir, Lake Houston, Texas

Results of measurements of light penetration at sites in Lake Houston near Houston, Texas, indicate that light-extinction coefficients during 1989– 90 range from about 2.49 to 7.93 meters-1 and euphotic zone depth ranges from about 0.61 to 1.85 meters. The coefficients are largest near the inflow site of West Fork San Jacinto River (upstream) and decrease slightly toward the dam (downstream). Total suspended solids and total organic carbon concentrations also are largest at the upstream end. Chlorophyll a+b concentrations are smallest near the dam, increase slightly upstream, and are largest during growing-season months. Color and turbidity show the strongest correlations with light-extinction coefficients in Lake Houston. Dissolved phosphorus and nitrogen concentrations are greater than growth-limiting concentrations during the study period, indicating that nutrient availability did not limit primary productivity or the phytoplankton biomass in Lake Houston. Light-extinction coefficients in relation to selected water-quality constituents indicate that more than one constituent affects the light-attenuating properties of Lake Houston. Attenuation of light in water depends on total suspended solids for predominant light scattering and on dissolved organic matter (color) and chlorophyll a+b for absorption of light. A statistical analytical model using Spearman rank order correlation shows that color and turbidity are the most useful water-quality constituents sampled to determine light-attenuating properties of water in Lake Houston. Multiple-regression analysis of measured light-extinction coefficients as the dependent variable and measured color and turbidity as independent variables for water from Lake Houston produced the relation: light-extinction coefficient (η) = 2.78 + 0.007 X color + 0.036 X turbidity, with an average error of the computed coefficient to measured value of ±13 percent. The model can be useful in computing the thickness of the euphotic zone to determine primary productivity in the reservoir.

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USGS1997

Time of travel of solutes in the Sabine River basin, Texas, August-November 1996

The U.S. Geological Survey (USGS), in cooperation with the Sabine River Authority, did a time-of-travel study in the Sabine River Basin during low flow from August to November 1996. The study was done to provide accurate estimates of the time-of-travel and dispersion characteristics for solutes during low flow in a 1.8-mile (mi) reach of Grace Creek, a 23.9-mi reach of the mainstem Sabine River, a 3.4-mi reach of Hawkins Creek, and a 1.9-mi reach of Rocky Creek. This report explains the approach and documents the results of the study. The results of the study will be used by the Texas Natural Resource Conservation Commission in a water-quality model to determine waste-load allocation in Segment 0505 of the Sabine River Basin. The time-of-travel and dispersion characteristics also provide useful information on the probable behavior of soluble contaminants that might be introduced into the streams measured in this study.

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