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G. B. Ozuna

Publications and source records attributed to G. B. Ozuna.

6 recordsLinked to original sources
USGS1993

Ground-water conditions in Pecos County, Texas, 1987

A comparison of 1987 water levels with historical (1940-49) water levels in the Edwards-Trinity (Plateau) aquifer indicated that water levels declined more than 50 feet in three locations in the Leon-Belding irrigation area, in an area north of Fort Stockton, and in a well east of Bakersfield. Maximum measured declines were 54 and 82 feet in the Leon-Belding irrigation area. The maximum measured rise was 55 feet in one well in east-central Pecos County. The chemical quality of water in the Edwards-Trinity aquifer of Pecos County varied greatly during 1987. Most wells in the eastern, southern, and southwestern parts of the county had water with a specific conductance of 1,000 μ S/cm (microsiemens per centimeter at 25 °C) or less. Three areas that had anomalously large specific conductances in ground water in north-central Pecos County are associated with water issuing from Santa Rosa, Diamond Y, and Comanche Springs. Specific conductance in water from wells and springs ranged from 311 μ S/cm in south-central Pecos County to 9,600 μ S/cm in the north. Dissolved sulfate concentrations ranged from 17 to 2,300 mg/L (milligrams per liter), and dissolved chloride concentrations ranged from 12 to 1,400 mg/L. Dissolved-solids concentrations ranged from 251 to 5,580 mg/L. Total nitrite plus nitrate concentrations (considered to be all nitrate for this report) ranged from less than 0.1 to 8.9 mg/L. Chemical water types range from calcium bicarbonate to calcium sulfate to sodium chloride. Historical (1940-49) and 1987 dissolved-solids concentrations were compared to identify potential changes in water quality. In some local areas, dissolved-solids concentrations decreased as much as 1,630 mg/L. The increase in dissolved-solids concentrations in water from wells and springs ranged from 5 to 4,894 mg/L. Maximum increases in dissolved-solids concentrations were 3,290 mg/L in water from Comanche Springs and 4,894 mg/L in water from Santa Rosa Springs. The increases may represent a mixing of Edwards-Trinity water with moderately saline water from underlying rocks of Permian age, or an accumulation of salts from surface-water sources. Comanche Springs, dry since 1961, began flowing again in October 1986, following several weeks of record or near-record precipitation in Fort Stockton and the Trans-Pecos region. Accelerated recharge from the increased precipitation, combined with a cessation of irrigation pumpage in August 1986, probably were responsible. The springs ceased flowing in May 1987, following the start of irrigation pumpage in February 1987. Correlation between flow from Comanche Springs and water levels in Fort Stockton city well no. 2 in the Leon-Belding irrigation area indicates that the springs are unlikely to flow when the depth to water in this well exceeds about 232 feet.

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USGS1993

Reconnaissance investigation of the geology and hydrogeology of Lackland Air Force Base, San Antonio, Texas

An investigation at Lackland Air Force Base and Lackland Air Force Base Training Annex (Medina Base) was conducted from May to September 1988 to delineate the subsurface geology, to describe the hydrogeology within the study area, and to determine possible migration pathways for contaminants. Data from this investigation supplement data collected in conjunction with other Air Training Command studies conducted under the Installation Restoration Program. The geologic formations in the vicinity of Lackland Air Force Base and Medina Base consist of sedimentary rocks of Cretaceous, Tertiary, and Quaternary age. The lithology of these formations consists primarily of limestone and marl, with lesser amounts of gravel, sand, silt, shale, and clay. The formations that comprise the geologic setting at Lackland Air Force Base and Medina Base include the Navarro Group of Late Cretaceous age, the Midway Group and Uvalde Gravel of Tertiary age, and the Leona Formation and fluviatile terrace deposits of Quaternary age. The age of the faulting within the study area has not been determined accurately, but the faulting might have occurred during intervals from Early Cretaceous to Holocene time. During these tectonic episodes, uplift of the Edwards Plateau might have occurred. This uplift could have enhanced erosion of the Cretaceous age Edwards Group, which is north of the study area, causing deposition of alluvial deposits south of this tectonic activity. The Leona Formation is composed of limestone gravel deposits forming terraces in the valleys of present streams. In general, these terraces are topographically lower than those formed by the Uvalde Gravel. In contrast, the fluviatile terrace deposits are above flood level along entrenched streams such as Leon and Medio Creeks. The Leona Formation is generally above the level of these fluviatile terrace deposits. A review of the hydrogeologic literature indicated that the Navarro and Midway Groups do not yield water to wells in Bexar County. However, recent studies by the U.S. Geological Survey at Kelly Air Force Base indicate that the uppermost beds of the Navarro Group can be saturated but yield little or no water to wells. Each stream terrace deposit of the Leona Formation and the fluviatile terrace deposits are separate water-bearing units. At Lackland Air Force Base, shallow ground water is present in the Leona Formation and the flow probably is toward Leon Creek. At Medina Base, the fluviatile terrace deposits are present along both banks of Medio Creek and probably are separate water-bearing units. Furthermore, ground-water flow in each of these units probably is toward Medio Creek. The Uvalde Gravel, present only at and west of Medina Base, is not a source of shallow ground water. However, during periods of precipitation, the formation can readily absorb precipitation and surface runoff. Water drains quickly through the formation because of its topographically high position and substantial hydraulic conductivity. Major pathways of potential contaminant migration off the bases include the local streams of Medio and Leon Creeks, and to a lesser extent, the shallow ground water beneath the bases. Although the Uvalde Gravel is not a source of shallow ground water at Medina Base, it drains water quickly, and wastes that might be buried in the gravel could be a potential source of contamination during brief ground-water recharge periods resulting from major precipitation.

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USGS1984

Compilation of hydrologic data for the Edwards Aquifer, San Antonio area, Texas, 1981, with 1934-81 summary

The average annual ground-water recharge to the Edwards aquifer in the San Antonio area, Texas, from 1934 through 1981, was 612,400 acre-feet. The recharge in 1981 was 1,448,400 acre-feet, which is the third highest annual recharge since 1934. A maximum annual recharge of 1,711,200 acre-feet occurred in 1958, and a minimum annual recharge of 43,700 acre-feet occurred in 1956. The calculated annual discharge by wells and springs in 1981 was 794,400 acre-feet. Annual discharge by wells and springs ranged from a maximum of 960,900 acre-feet in 1977 to a minimum of 388,800 acre-feet in 1955. The annual discharge by wells was 387,100 acre-feet in 1981. Although water levels in many of the wells in the Edwards aquifer fluctuated near the midpoint between record high and low levels during the first 5 months of 1981, the volume of ground water in storage in the aquifer was above average for most of the year. Analyses of water samples from 56 wells and 3 springs show that the water is of a significantly better quality than the level established for public water systems.

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