Publications

The Edwards aquifer in south-central Texas is one of the most productive aquifers in the Nation and is the primary source of water for the rapidly growing San Antonio area. Springs issuing from the Edwards aquifer provide habitat for several threatened and endangered species, serve as locations for recreational activities, and supply downstream users. Comal Springs and San Marcos Springs are major

The hydrogeology, distribution, and volume of saline water in 22 aquifers in the southern midcontinent of the United States were evaluated to provide information about saline groundwater resources that may be used to reduce dependency on freshwater resources. Those aquifers underlie six States in the southern midcontinent—Arkansas, Kansas, Louisiana, Missouri, Oklahoma, and Texas—and adjacent area

Despite bans on PCB use since 1975 (open systems) and 1987 (closed systems), concentrations of PCBs in riverine fish in France continue to exceed regulatory levels. We present historical records of PCB concentrations in sediment cores from eight sites on the Rhône River, from Lake Geneva to the Mediterranean Sea. Maximum PCB concentrations (sum of seven indicator PCBs) increase downstream, from 11

The freshwater zone of the San Antonio segment of the Edwards aquifer is used by residents of San Antonio and numerous other rapidly growing communities in south-central Texas as their primary water supply source. This freshwater zone is bounded to the south and southeast by a saline-water zone with an intermediate zone transitioning from freshwater to saline water (transition zone). As demands on

The U.S. Geological Survey (USGS) in cooperation with the Harris-Galveston Subsidence District, City of Houston, Fort Bend Subsidence District, Lone Star Groundwater Conservation District, and Brazoria County Groundwater Conservation District has produced a series of annual reports depicting groundwater-level altitudes in the Chicot, Evangeline, and Jasper aquifers of the Gulf Coast aquifer system

The Edwards aquifer is the primary source of potable water for the San Antonio area in south-central Texas. The Knippa Gap was postulated to channel or restrict flow in the Edwards aquifer in eastern Uvalde County, and its existence was based on a series of numerical simulations of groundwater flow in the aquifer. To better understand the function of the area known as the Knippa Gap as it pertains

The High Plains aquifer underlies almost 112 million acres in the central United States. It is one of the largest aquifers in the Nation in terms of annual groundwater withdrawals and provides drinking water for 2.3 million people. The High Plains aquifer has gained national and international attention as a highly stressed groundwater supply primarily because it has been appreciably depleted in so

The U.S. Geological Survey (USGS), in cooperation with the Northeast Texas Municipal Water District and the Texas Commission on Environmental Quality, did a baseline assessment in 2010-11 of physical characteristics and selected aquatic biota (fish and mussels) collected at the mesohabitat scale for three stream reaches in the Big Cypress Basin in northeastern Texas for which environmental flows h

Simply stated, groundwater recharge is the addition of water to the groundwater system. Most of the water that is potentially available for recharging the groundwater system in Montgomery and adjacent counties in southeast Texas moves relatively rapidly from land surface to surface-water bodies and sustains streamflow, lake levels, and wetlands. Recharge in southeast Texas is generally balanced by

Wetlands are widely recognized as sentinels of global climate change. Long-term monitoring data combined with process-based modeling has the potential to shed light on key processes and how they change over time. This paper reports the development and application of a simple water balance model based on long-term climate, soil, vegetation and hydrological dynamics to quantify groundwater–surface w

The Trinity aquifer is an important source of groundwater in central Texas, including Bexar County, where population growth has resulted in an increased demand for water (Ashworth, 1983; Mace and others, 2000). Numerous springs issue from rock outcrops within and surrounding the Trinity aquifer in northern Bexar County (fig. 1). The effects of increased groundwater withdrawals from the Trinity aqu

The composition, occurrence, distribution, and possible toxicity of chemical mixtures in the environment are research concerns of the U.S. Geological Survey and others. The presence of specific chemical mixtures may serve as indicators of natural phenomena or human-caused events. Chemical mixtures may also have ecological, industrial, geochemical, or toxicological effects. Chemical-mixture occurre