Publications

The stratigraphic units of the Edwards aquifer in south-central Uvalde County generally are porous and permeable. The stratigraphic units that compose the Edwards aquifer in south-central Uvalde County are the Devils River Formation in the Devils River trend; and the West Nueces, McKnight, and Salmon Peak Formations in the Maverick Basin. The Balcones fault zone is the principal...

No abstract available.

Water-quality trends reflect the relation between water quality and human activities, chronicling changes in concentrations of environmental contaminants, introduction of new contaminants, and successful efforts in environmental pollution remediation. Historical data available for analyzing trends often have severe limitations, from questionable accuracy to unknown sampling and analytic

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...

San Marcos Springs is the second largest spring in Texas and is the headwaters for the San Marcos River in San Marcos. Spring Lake (fig. 1) was built in 1848 at the site of a marsh formed by the springs to provide hydropower to a mill. The San Marcos River originates from the 15-acre lake and flows approximately 4 river miles (mi) south to its confluence with the Blanco River. The mean...

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...

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...

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...

Comal Springs of Central Texas are the largest springs in the southwestern United States. The long-term average flow of the Comal River, which essentially is the flow from Comal Springs, is 284 cubic feet per second (ft3/s). The artesian springs emerge at the base of an escarpment formed by the Comal Springs fault. The Comal River (fig. 1) is approximately 2 miles (mi) long and is a...

This report, prepared in cooperation with the Fort Bend Subsidence District, presents maps for the Chicot and Evangeline aquifers in Fort Bend County and adjacent areas showing the approximate water-level altitudes in wells in 1990 (figs. 1, 2). The most recent previously published water-level-altitude maps (and water-level-change maps) for the two aquifers are by Coplin and others (1997...

This report is one in an annual series of reports that depicts water-level altitudes and water-level changes since 1977 and compaction since 1973 in the Chicot and Evangeline aquifers in the Houston-Galveston region, Texas.

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...