Publications

Sources of trends in water-quality data for selected streams in Texas for the 1975-89 water years were investigated in this study. The investigation of sources was confined to distinct geographic patterns in the trend indicators for one constituent or for a group of related constituents. The probable source of trend patterns in nutrients and measures of oxygen in the Trinity River Basin was change

Measurements of water levels from wells completed in the Chicot and Evangeline aquifers were used to construct maps showing approximate changes of water levels in Fort Bend County and adjacent areas during 1990-94 and 1993-94.

The Edwards-Trinity aquifer system underlies about 42,000 square miles of west-central Texas. Nearly flat-lying, mostly Comanche (Lower Cretaceous) strata of the aquifer system thin northwestward atop massive pre-Cretaceous rocks that are comparatively impermeable and structurally complex. From predominately terrigenous clastic sediments in the east and fluvialdeltaic (terrestrial) deposits in the

This report is one in a series of reports that depict water-level changes since 1977 and compaction of subsurface material since 1973.  The report was prepared in cooperation with the City of Houston and the Harris-Galveston Coastal Subsidence District, and presents maps showing the approximate changes in water levels in wells completed in the Chicot and Evangeline aquifers, 1977-94 and 1993-94 (f

All of the hydrogeologic subdivisions within the Edwards aquifer outcrop in Comal County have some porosity and permeability. The most porous and permeable appear to be hydrogeologic subdivision VI, the Kirschberg evaporite member of the Kainer Formation; hydrogeologic subdivision III, the leached and collapsed members, undivided; and hydrogeologic subdivision II, the cyclic and marine members, un

The Edwards-Trinity aquifer system is currently (1993) being studied as part of the Regional Aquifer-Systems Analysis program. A major goal of the project is to understand and describe the regional ground-water flow system. A finite-element model for simulating two-dimensional steady-state ground-water flow was applied to the major aquifers of the Edwards-Trinity aquifer system and contiguous hydr

Many researchers have studied the downdip limit of freshwater in the Edwards aquifer or various aspects of the saline-water zone and its relation to the freshwater zone. These studies were summarized and used to synthesize a consistent hydrologic and geochemical framework from which to interpret data from field studies. The concept derived from the previous work on the downdip limit of the freshwa

In 1991, the U.S. Geological Survey (USGS), Department of the Interior, began a National Water-Quality Assessment (NAWQA) Program. The long-term goals of the NAWQA Program are to describe the status of and trends in the quality of a large, representative part of the Nation's surface- and ground-water resources and to identify the major natural and human factors that affect the quality of these res

Samples of ground water and tertiary-treated water were evaluated to determine the distribution of injected water and trihalomethane compounds in the Hueco bolson aquifer near El Paso, Texas. Chloride and nitrate concentrations and oxygen-18/oxygen-16 (δ18O) values were used with end-member mixing analysis to estimate the fractional contributions of injected water, irrigation-affected water, salin

This report presents 1990 freshwater withdrawal estimates for Texas by source and category. Withdrawal source is either ground water or surface water. Withdrawal categories include: self-supplied irrigation, thermoelectric-power generation, water supply, industrial and mining, and other (domestic, commercial, livestock). Withdrawal data are aggregated by county, major aquifer, and principal river

Much of the Edwards-Trinity aquifer system contains freshwater, but sizable parts contain marginally fresh or slightly saline water. The predominant water type in the aquifer system is calcium bicarbonate; however, one of seven other hydrochemical facies characterizes the water in places. The median dissolved-solids concentration of water samples from the Edwards aquifer in the Balcones fault zone

The upper Colorado River and some of its tributaries between Lake J.B. Thomas and O.H. Ivie Reservoir contain saline water (defined as water having dissolved-solids concentrations greater than 1,000 milligrams per liter). Dissolved-solids loads at nine streamflow water-quality stations increased from 1986 to 1988. The largest increases were in Beals Creek and in the Colorado River downstream from