Search USGS⌕ Search

Geology topics

Stanley G. Robson

Publications and source records attributed to Stanley G. Robson.

24 records · Page 2Linked to original sources
USGS1978

Application of digital profile modeling techniques to ground-water solute transport at Barstow, California

This study investigated the use of a two-dimensional profile-oriented water-quality model for the simulation of head and water-quality changes through the saturated thickness of an aquifer. The profile model is able to simulate confined or unconfined aquifers with nonhomogeneous anisotropic hydraulic conductivity, nonhomogeneous specific storage and porosity, and nonuniform saturated thickness. An aquifer may be simulated under either steady or nonsteady flow conditions provided that the ground-water flow path along which the longitudinal axis of the model is oriented does not move in the aquifer during the simulation time period. The profile model parameters are more difficult to quantify than are the corresponding parameters for an areal-oriented water-fluality model. However, the sensitivity of the profile model to the parameters may be such that the normal error of parameter estimation will not preclude obtaining acceptable model results. Although the profile model has the advantage of being able to simulate vertical flow and water-quality changes in a single- or multiple-aquifer system, the types of problems to which it can be applied is limited by the requirements that (1) the ground-water flow path remain oriented along the longitudinal axis of the model and (2) any subsequent hydrologic factors to be evaluated using the model must be located along the land-surface trace of the model. Simulation of hypothetical ground-water management practices indicates that the profile model is applicable to problem-oriented studies and can provide quantitative results applicable to a variety of management practices. In particular, simulations of the movement and dissolved-solids concentration of a zone of degraded ground-water quality near Barstow, Calif., indicate that halting subsurface disposal of treated sewage effluent in conjunction with pumping a line of fully penetrating wells would be an effective means of controlling the movement of degraded ground water.

Water Supply Paper↗
USGS1977

Application of digital profile modeling techniques to ground-water solute transport at Barstow, California

This study investigated the use of a two-dimensional profile-oriented water-quality model for the simulation of head and water-quality changes through the saturated thickness of an aquifer. The profile model is able to simulate confined or unconfined aquifers with nonhomogeneous anisotropic hydraulic conductivity, nonhomogeneous specific storage and porosity, and nonuniform saturated thickness. An aquifer may be simulated under either steady or nonsteady flow conditions provided that the ground-water flow path along which the longitudinal axis of the model is oriented does not move in the aquifer during the simulation time period. The profile model parameters are more difficult to quantify than are the corresponding parameters for an areal-oriented water-quality model. However, the sensitivity of the profile model to the parameters may be such that the normal error of parameter estimation will not preclude obtaining acceptable model results. Although the profile model has the advantage of being able to simulate vertical flow and water-quality changes in a single- or multiple-aquifer system, the types of problems to which it can be applied is limited by the requirements that (1) the ground-water flow path remain oriented along the longitudinal axis of the model and (2) any subsequent hydrologic factors to be evaluated using the model must be located along the land-surface trace of the model. Simulation of hypothetical ground-water management practices indicates that the profile model is applicable to problem-oriented studies and can provide quantitative results applicable to a variety of management practices. In particular, simulations of the movement and dissolved-solids concentration of a zone of degraded ground-water quality near Barstow, Calif., indicate that halting subsurface disposal of treated sewage effluent in conjunction with pumping a line of fully penetrating wells would be an effective means of controlling the movement of degraded ground water.

California↗
USGS1977

Ground-water quality near a sewage-sludge recycling site and a landfill near Denver, Colorado

The Metropolitan Denver Sewage Disposal District and the City and County of Denver operate a sewage-sludge recycling site and a landfill in an area about 15 miles (24 kilometers) east of Denver. The assessment of the effects of these facilities on the ground-water system included determining the direction of ground-water movement in the area, evaluating the impact of the wastedisposal activities on the chemical quality of local ground water, and evaluating the need for continued water-quality monitoring. Surficial geology of the area consists of two principal units: (1) Alluvium with a maximum thickness of about 25 feet (7.6 meters) deposited along stream channels, and (2) bedrock consisting of undifferentiated Denver and Dawson Formations. Ground water in formations less than 350 feet (110 meters) deep moves to the north, as does surface flow, while ground water in formations between 570 and 1,500 feet (170 and 460 meters) deep moves to the west. Estimates of ground-water velocity were made using assumed values for hydraulic conductivity and porosity, and the observed hydraulic gradient from the study area. Lateral velocities are estimated to be 380 feet (120 meters) per year in alluvium and 27 feet (8.2 meters) per year in the upper part of the bedrock formations. Vertical velocity is estimated to be 0.58 foot (0.18 meter) per year in the upper part of the bedrock formations. Potentiometric head decreases with depth in the bedrock formations indicating a potential for downward movement of ground water. However, waterquality analysis and the rate and direction of ground-water movement suggest that ground-water movement in the area is primarily in the lateral rather than the vertical direction. Five wells perforated in alluvium were found to have markedly degraded water quality. One well was located in the landfill and water that was analyzed was obtained from near the base of the buried refuse, two others were located downgradient and near sewage-sludge burial areas, and the remaining two are located near stagnant surface ponds. Concentrations of nitrate in wells downgradient from fields where sludge is plowed into the soil were higher than background concentrations due to the effects of the sludge disposal. No evidence of water-quality degradation was detected in deeper wells perforated in the bedrock formations. Continued water-quality monitoring is needed because of the continuing disposal of wastes. A suggested monitoring program would consist of monitoring wells near the landfill twice a year and monitoring wells near the sludge-disposal areas on an annual basis.

Colorado↗
USGS1972

Water-resources investigation using analog model techniques in the Saugus-Newhall area, Los Angeles County, California

The Saugus-Newhall area is in the upper Santa Clara River valley, in northwestern Los Angeles. County, about 30 miles north of Los Angeles. The area has two main aquifers, the alluvial aquifer and the underlying Saugus aquifer. These two aquifers are the subject of this investigation. The alluvial aquifer consists of river channel alluvium as much as 200 feet thick with a transmissibility ranging from 50,000 to 325,000 gallons per day per foot and a storage coefficient of i0 to 20 percent. In 1945 about 210,000 acre-feet of recoverable ground water was in storage in the alluvial aquifer. The alluvial aquifer is the major source of ground-water pumpage and has supplied about 600,000 acre-feet of effective pumpage during the period 1945 through 1967. Ground-water pumpage and variations in the quantities of surface-water recharge have caused large fluctuations in the water levels in the alluvial aquifer. The Saugus aquifer has. a maximum saturated thickness of about 3,500 feet and ranges in transmissibility from 2,000 to 200,000 gallons per day per foot. Based on limited available data, the Saugus aquifer may contain as much as 6 million acre-feet of ground water in storage under steady-state conditions. Meager available data indicate the water quality in some areas of the Saugus aquifer is poor so that only a fraction of the ground water in storage in the aquifer may be usable for domestic water supplies. Floodflow in the streams in the area is the major source of recharge to the alluvial aquifer and the underlying Saugus aquifer. The chemical quality of the ground water is largely dependent on the chemical quality of the surface-water recharge. Ground-water discharge occurs along the Santa Clara River below Castaic Junction. Water will be imported to supplement the existing water resources. An analog model of the ground-water basin indicates that it will not be possible to artificially recharge the proposed quantities of imported water into the alluvial aquifer above Saugus unless ground-water pumpage from that area is increased. The model further indicates that the alluvial aquifer may not be able to supply enough water, even when artificially recharged with imported water, to meet the estimated maximum pumping rate to 1990 used in the model and that increased pumpage from the Saugus aquifer may cause water-level declines in both aquifers and may eliminate the natural ground-water discharge from the aquifers.

Open-File Report↗