Geology topics

A. S. Navoy

Publications and source records attributed to A. S. Navoy.

14 recordsLinked to original sources

USGS1994

Documentation of a computer program to simulate transient leakage from confining units using the modular finite-difference, ground-water flow model

Transient leakage into or out of a compressible fine-grained confining unit results from ground- water storage changes within the unit. The computer program described in this report provides a new method of simulating transient leakage using the U.S. Geological Survey modular finite- difference ground-water flow model (MODFLOW). The new program is referred to as the Transient- Leakage Package. The Transient-Leakage Package solves integrodifferential equations that describe flow across the upper and lower boundaries of confining units. For each confining unit, vertical hydraulic conductivity, thickness, and specific storage are specified in input arrays. These properties can vary from cell to cell and the confining unit need not be present at all locations in the grid; however, the confining units must be bounded above and below by model layers in which head is calculated or specified. The package was used in an example problem to simulate drawdown around a pumping well in a system with two aquifers separated by a confining unit. For drawdown values in excess of 1 centimeter, the solution using the new package closely matched an exact analytical solution. The problem also was simulated without the new package by using a separate model layer to represent the confining unit. That simulation was refined by using two model layers to represent the confining unit. The simulation using the Transient-Leakage Package was faster and more accurate than either of the simulations using model layers to represent the confining unit.

Open-File Report↗

USGS1994

Simulated effects of projected withdrawals from the Wenonah-Mount Laurel aquifer on ground-water levels in the Camden, New Jersey, area and vicinity

The Wenonah-Mount Laurel aquifer is being considered as a potential source of future water supply for the Camden, New Jersey, area. The deeper Potomac- Raritan-Magothy aquifer system is currently the major major source of water supply for the area, but its use may be curtailed or reduced by 35 percent of 1983 withdrawals through its designation by the New Jersey Department of Environmental Protection and Energy as "Water Supply Critical Area#2." Withdrawals from the Wenonah-Mount Laurel aquifer currently (1989) total about 7 million gallons per day. The anticipated use of this aquifer by communities with access to it, as an alternative supply, could increase to more than 14 million gallons per day by 2020. If the communities of Clayton and Glassboro decrease their withdrawals from the Potomac-Raritan-Magothy aquifer system by 50 percent or cease them entirely because of their proximity to saline water, the use of Wenonah-Mount Laurel aquifer could increase to greater than 15 million gallons per day by 2020. Simulation of the ground-water system indicates that the projected increase in withdrawals will cause cones of depression in the potentiometric surface of the Wenonah-Mount Laurel aquifer in the Camden metro- politan area by 2020 that extend to depths ranging from 10 feet above sea level to 60 feet below sea level. This represents a secline of about 40 to 100 feet thr 1990 conditions. Withdrawals in northeastern Burlington County will cause a large cone of depression that, by 2020, will extend to depths of about 220 feet below sea level, represent- ing a decline of about 140 feet from 1990 conditions. Simulation results indicate that water levels in the Wenonah-Mount Laurel aquifer near the Salem Nuclear Power Plant are somewhat insensitive to withdrawals elsewhere in the aquifer. In some areas, especially in Burlington County, the cones of depression have developed in proximity to the aquifer-outcrop area and could induce infiltration from streams crossing the outcrop. Because of the hydraulic connection to adjacent aquifers, future management plans need to be developed in a compre- hensive manner with regard to all aquifers. Further study of the aquifer in Salem County could provide additional information on the hydraulic connection to Delaware Bay and the potential for saltwater intrusion.

New Jersey↗

USGS1987

Ground-water resources of Flagler County, Florida

Groundwater is the only significant source of potable water in Flagler County. Usable water occurs in the Upper Floridan aquifer, the intermediate population is expected to place stresses on the water resources of the county. Although rainfall averages almost 50 in/yr, most of the water leaves as evapotranspiration and streamflow. Less than 1 in/yr recharge may be occurring to the Upper Floridan aquifer, the highest yielding aquifer. The Upper Floridan aquifer consists of the Avon Park Formation, the Ocala Limestone, and the basal dolomitic limestone of the Hawthorne. Use of the Upper Floridan aquifer for public water supply is limited in most of the county because it contains marginally potable or brackish water. It is used extensively for agricultural irrigation. The intermediate aquifer system consists of thin, discontinues lenses of sand, shell, and limestone between clays overlying the Floridan aquifer system. The intermediate aquifer system is an important part of the public water supply of the county because of the good quality of the water. The intermediate aquifer system has variable yields because of the discontinuous lenses. The surficial aquifer system is composed of sand and shell with varying fractions of finer materials. Well yields are small in the west and central parts of Flagler County, but the surficial aquifer system is an adequate source of domestic supply on the barrier island. A zone of freshwater in the surficial aquifer system is very important in the Hammock area, being the local source of most domestic supply in the area. Changes in hydrologic conditions from the 1950 's include a long-term decline in water levels in the Upper Floridan aquifer coincident with lower-than-average rainfall and a greater seasonal fluctuation of water levels. Chloride concentrations of water in the Upper Floridan aquifer do not appear to have changed significantly, presently ranging from 7 to 3,700 mg/L. Development will place stress on the aquifers and may result in upconing of brackish water in pumping centers and in lateral saltwater intrusion in coastal areas. (Author 's abstract)

Water-Resources Investigations Report↗

USGS1986

Hydrogeologic data from a 2,000-foot deep core hole at Polk City, Green Swamp area, central Florida

Two core holes were drilled to depths of 906 and 1,996 feet, respectively, within the Tertiary limestone (Floridan) aquifers, at Polk City, central Florida. Data from the two holes revealed that the bottom of the zone of vigorous groundwater circulation is confined by carbonate rocks at a depth of about 1,000 feet (863 feet below sea level). The zone of circulation is divided into two high-permeability zones. The dissolved solids of the water within the high-permeability zones is approximately 150 milligrams per liter. Within the carbonate rocks, the dissolved solids content of the water reaches about 2,000 milligrams per liter at the bottom of the core hole. Water levels in the core holes declined a total of about 16 feet as the hole was drilled; most of the head loss occurred at depths below 1,800 feet. The porosities of selected cores ranged from 1.6 to 45.3 percent; the hydraulic conductivities ranged from less than 0.000024 to 19.0786 feet per day in the horizontal direction and from less than 0.000024 to 2.99 feet per day in the vertical direction; and the ratio of vertical to horizontal permeability ranged from 0.03 to 1.98. Due to drilling problems, packer tests and geophysical logging could not be accomplished. (USGS)

Water-Resources Investigations Report↗

USGS1981

Potentiometric surface of the Floridan Aquifer in central Sumter County, Florida, May 1981

This map presents the potentiometric surface of the Floridan aquifer in central Sumter County, Fla., for May 1981. The Floridan aquifer is the principal source of potable water in the area. The focus of the map is the potentiometric surface in the Jumper Creek Canal area for the low water-level period. Water-level measurements were made on approximately 60 wells. The potentiometric surface ranged in altitude from more than 90 feet in the southeast part of the county to less than 35 feet northwest of Lake Panasoffkee in the west central area. (USGS)

Open-File Report↗

USGS1981