USGS Science⌕ Search

Geology topics

P.L. Rettman

Publications and source records attributed to P.L. Rettman.

13 recordsLinked to original sources
USGS1992

Evaluation of the use of remote-sensing data to identify crop types and estimate irrigated acreage, Uvalde and Medina counties, Texas, 1989

Remote-sensing data were used to estimate that 190,000 acre-feet of water was pumped from the Edwards aquifer in 1989 to irrigate crops in Uvalde and Medina Counties. Landsat digital satellite images for March and July 1989 were combined and classified to identify the areas of crops irrigated with water from the Edwards aquifer in the two counties. Normalized difference, the difference between the infrared and red reflectance values divided by the total of those values, was used to discriminate vegetative from nonvegetative ground cover. The images subsequently were classified using maximum likelihood, an unsupervised classification procedure. Detailed vegetation distribution maps of two calibration sites in the study area, and boundaries of the areas probably irrigated in 1989, helped to interpret the results and to separate probable irrigated areas from the rest of the image. Results were verified using crop acreages reported by the U.S. Department of Agriculture, Agricultural Stabilization and Conservation Service (ASCS). The total areas for all irrigated crops estimated using remote-sensing data were about 8 percent higher for Uvalde County and about 4 percent higher for Medina County than the areas reported by the ASCS. Irrigated-crop areas subsequently were multiplied by the respective duties of water to calculate the total quantity of water pumped from the aquifer for irrigation. Pumpage did not differ for the two estimates of crop areas for Uvalde County and differed by about 3 percent for Medina County.

Texas↗
USGS1984

Ground-water resources of Limestone County, Texas

Limestone County, located in east-central Texas, has small to plentiful ground-water supplies available, depending upon the location within the county. The Wilcox Group in the eastern part of the county has adequate supplies to meet the expected water demands in the foreseeable future. The thicker zones of the Wilcox Group can supply yields in excess of 500 gallons per minute. The Midway Group can supply yields in excess of 100 gallons per minute from the Tehuacana Member of the Kincaid Formation. This represents the largest well yields from the Midway Group in Texas. The Midway Group elsewhere in the State is mostly a poor water producer and is not considered an aquifer. The Taylor Marl and Navarro Group furnish only small quantities of ground water to wells in the western part of the county where these units crop out. The Hosston and Travis Peak Formations are present at depths in excess of 2,000 feet. These formations, which contain slightly saline water in the western part of the county, could be expected to produce water with a temperature of about 150°F that might be used for heating purposes. About 0.9 million gallons per day of ground water was used for all purposes in 1980. This use has declined since 1955 but is expected to increase as additional public-supply and industrial wells are being developed. The Wilcox Group is capable of annually yielding at least 14,000 acre-feet or 11.6 million gallons per day of water to wells on a long-term basis. Generally, the ground water is of acceptable quality for most uses. Relatively high dissolved-solids and iron concentrations are the major water-quality problems. Water-quality problems that may be the result of man's activities are limited to a small oilfield area near Mexia. Lignite mining from the Wilcox Group is expected to take place in the foreseeable future. The collection of additional hydrologic data on the Wilcox would be desirable before, during, and after mining.

Texas↗
USGS1980

Hydrochemical data for the Edwards aquifer in the San Antonio area, Texas

This report presents hydrochemical data that was collected as part of the investigations of the Edwards aquifer in the San Antonio area, Te xas, during 1970-78 and indicates other sources of available data. The report includes the results of chemical analyses of 159 water samples from 123 well s and springs; tritium analyses for 242 water samples from 120 wells and springs; isotope and redox-potential analyses of 31 water samples from wells, springs, and streams; and calculated dissolved carbonate, partial C02 pressures, and saturation indices of selected minerals in 98 water samples from 81 wells, springs, and streams. The water types and hydrochemical facies are given for six zones of the aquifer.

Texas Department of Water Resources Report↗