Keith J Halford (Former Employee)
Science and Products
Filter Total Items: 63
Hydrogeology, water quality, and simulated effects of ground-water withdrawals from the Floridan aquifer system, Seminole County and vicinity, Florida
The hydrogeology and ground-water quality of Seminole County in east-central Florida was evaluated. A ground-water flow model was developed to simulate the effects of both present day (September 1996 through August 1997) and projected 2020 ground-water withdrawals on the water levels in the surficial aquifer system and the potentiometric surface of the Upper and Lower Floridan aquifers in Seminole
Authors
Rick M. Spechler, Keith J. Halford
Problems associated with estimating ground water discharge and recharge from stream-discharge records
Ground water discharge and recharge frequently have been estimated with hydrograph-separation techniques, but the critical assumptions of the techniques have not been investigated. The critical assumptions are that the hydraulic characteristics of the contributing aquifer (recession index) can be estimated from stream-discharge records; that periods of exclusively ground water discharge can be rel
Authors
K. J. Halford, G.C. Mayer
Effects of steady-state assumption on hydraulic conductivity and recharge estimates in a surficial aquifer system
The ability of a calibrated flow model to predict the behavior of a surficial aquifer system is governed by the quality of the hydraulic conductivity and recharge estimates used. Reasonable lateral and vertical hydraulic conductivities can be estimated by steady-state simulations driven by effective recharge rates that approximate the net effects of evapotranspiration, and water released from stor
Authors
K. J. Halford
Simulated effects of projected ground-water withdrawals in the Floridan aquifer system, greater Orlando metropolitan area, east-central Florida
Ground-water levels in the Floridan aquifer system within the greater Orlando metropolitan area are expected to decline because of a projected increase in the average pumpage rate from 410 million gallons per day in 1995 to 576 million gallons per day in 2020. The potential decline in ground-water levels and spring discharge within the area was investigated with a calibrated, steady-state, ground-
Authors
Louis C. Murray, Keith J. Halford
Ground-water flow in the surficial aquifer system and potential movement of contaminants from selected waste-disposal sites at Naval Station Mayport, Florida
Ground-water flow through the surficial aquifer system at Naval Station Mayport near Jacksonville, Florida, was simulated with a two-layer finite-difference model as part of an investigation conducted by the U.S. Geological Survey. The model was calibrated to 229 water-level measurements from 181 wells during three synoptic surveys (July 17, 1995; July 31, 1996; and October 24, 1996). A quantifiab
Authors
K. J. Halford
Assessment of the potential effects of phytoremediation on ground-water flow around area C at Orlando Naval Training Center, Florida
No abstract available.
Authors
K. J. Halford
Ground-water flow in the surficial aquifer system and potential movement of contaminants from selected waste-disposal sites at Cecil Field Naval Air Station, Jacksonville, Florida
As part of the Installation Restoration Program, Cecil Field Naval Air Station, Jacksonville, Florida, is considering remedialaction alternatives to control the possible movement of contaminants from sites that may discharge to the surface. This requires a quantifiable understanding of ground-water flow through the surficial aquifer system and how the system will respond to any future stresses. Th
Authors
K. J. Halford
Hydrogeologic framework and simulation of ground-water flow and travel time in the shallow aquifer system in the area of Naval Support Activity Memphis, Millington, Tennessee
Naval Support Activity (NSA) Memphis is a Department of the Navy facility located at the City of Millington, Tennessee, about 5 miles north of Memphis. Contaminants have been detected in surface-water, sediment, and ground-water samples collected at the facility. As part of the Installation Restoration Program, the Navy is considering remedial-action options to prevent or lessen the effect of grou
Authors
James L. Robinson, John K. Carmichael, Keith J. Halford, David E. Ladd
Effects of unsaturated zone on aquifer test analysis in a shallow-aquifer system
A comparison between two hypothetical flow models of an unconfined aquifer, one saturated and the other variably saturated, indicates that the variably saturated model which explicitly models drainage from the unsaturated zone provides a better conceptual framework for analyzing unconfined aquifer test data and better estimates of the lateral and vertical hydraulic conductivity in fine-grained san
Authors
K. J. Halford
Hydrogeologic conditions and simulation of ground-water flow in the Greater Orlando Metropolitan Area, East-Central Florida
A finite-difference ground-water flow model was used to simulate the effects of both modern-day (1988) and projected 2010 ground-water withdrawals on the Floridan aquifer system in the greater Orlando metropolitan area. This area covers about 2,500 square miles and includes all of Orange and Seminole Counties and parts of Lake, Volusia, Brevard, Osceola, and Polk Counties. The hydrogeology of
Authors
L. C. Murray, K. J. Halford
Analysis of ground-water flow in the Catahoula aquifer system in the vicinity of Laurel and Hattiesburg, Mississippi
The upper, middle, and lower Catahoula aquifers in the vicinity of the cites of Laurel and Hattiesburg in southern Mississippi are made up of irregular, discontinuous sand zones in the Catahoula Formation of Miocene age. In places thee three aquifers may be hydraulically well connected, and are referred to as the Catahoula aquifer system. Withdrawal from the Catahoula aquifers increased from 28 mi
Authors
K. J. Halford, N. L. Barber
Potentiometric surface of the upper Floridan Aquifer in the St. Johns River Water Management District and vicinity, Florida, May 1994
This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for May 1994. The map is based on water-level measurements made at approximately 1,000 wells and several springs. Data on the map were contoured using 5-foot contour intervals in most areas. The potentiometric surface of this karstic aquifer generally reflects lan
Authors
D. M. Schiffer, A. M. O'Reilly, G. G. Phelps, L. A. Bradner, K. J. Halford, R. M. Spechler
Science and Products
Filter Total Items: 63
Hydrogeology, water quality, and simulated effects of ground-water withdrawals from the Floridan aquifer system, Seminole County and vicinity, Florida
The hydrogeology and ground-water quality of Seminole County in east-central Florida was evaluated. A ground-water flow model was developed to simulate the effects of both present day (September 1996 through August 1997) and projected 2020 ground-water withdrawals on the water levels in the surficial aquifer system and the potentiometric surface of the Upper and Lower Floridan aquifers in Seminole
Authors
Rick M. Spechler, Keith J. Halford
Problems associated with estimating ground water discharge and recharge from stream-discharge records
Ground water discharge and recharge frequently have been estimated with hydrograph-separation techniques, but the critical assumptions of the techniques have not been investigated. The critical assumptions are that the hydraulic characteristics of the contributing aquifer (recession index) can be estimated from stream-discharge records; that periods of exclusively ground water discharge can be rel
Authors
K. J. Halford, G.C. Mayer
Effects of steady-state assumption on hydraulic conductivity and recharge estimates in a surficial aquifer system
The ability of a calibrated flow model to predict the behavior of a surficial aquifer system is governed by the quality of the hydraulic conductivity and recharge estimates used. Reasonable lateral and vertical hydraulic conductivities can be estimated by steady-state simulations driven by effective recharge rates that approximate the net effects of evapotranspiration, and water released from stor
Authors
K. J. Halford
Simulated effects of projected ground-water withdrawals in the Floridan aquifer system, greater Orlando metropolitan area, east-central Florida
Ground-water levels in the Floridan aquifer system within the greater Orlando metropolitan area are expected to decline because of a projected increase in the average pumpage rate from 410 million gallons per day in 1995 to 576 million gallons per day in 2020. The potential decline in ground-water levels and spring discharge within the area was investigated with a calibrated, steady-state, ground-
Authors
Louis C. Murray, Keith J. Halford
Ground-water flow in the surficial aquifer system and potential movement of contaminants from selected waste-disposal sites at Naval Station Mayport, Florida
Ground-water flow through the surficial aquifer system at Naval Station Mayport near Jacksonville, Florida, was simulated with a two-layer finite-difference model as part of an investigation conducted by the U.S. Geological Survey. The model was calibrated to 229 water-level measurements from 181 wells during three synoptic surveys (July 17, 1995; July 31, 1996; and October 24, 1996). A quantifiab
Authors
K. J. Halford
Assessment of the potential effects of phytoremediation on ground-water flow around area C at Orlando Naval Training Center, Florida
No abstract available.
Authors
K. J. Halford
Ground-water flow in the surficial aquifer system and potential movement of contaminants from selected waste-disposal sites at Cecil Field Naval Air Station, Jacksonville, Florida
As part of the Installation Restoration Program, Cecil Field Naval Air Station, Jacksonville, Florida, is considering remedialaction alternatives to control the possible movement of contaminants from sites that may discharge to the surface. This requires a quantifiable understanding of ground-water flow through the surficial aquifer system and how the system will respond to any future stresses. Th
Authors
K. J. Halford
Hydrogeologic framework and simulation of ground-water flow and travel time in the shallow aquifer system in the area of Naval Support Activity Memphis, Millington, Tennessee
Naval Support Activity (NSA) Memphis is a Department of the Navy facility located at the City of Millington, Tennessee, about 5 miles north of Memphis. Contaminants have been detected in surface-water, sediment, and ground-water samples collected at the facility. As part of the Installation Restoration Program, the Navy is considering remedial-action options to prevent or lessen the effect of grou
Authors
James L. Robinson, John K. Carmichael, Keith J. Halford, David E. Ladd
Effects of unsaturated zone on aquifer test analysis in a shallow-aquifer system
A comparison between two hypothetical flow models of an unconfined aquifer, one saturated and the other variably saturated, indicates that the variably saturated model which explicitly models drainage from the unsaturated zone provides a better conceptual framework for analyzing unconfined aquifer test data and better estimates of the lateral and vertical hydraulic conductivity in fine-grained san
Authors
K. J. Halford
Hydrogeologic conditions and simulation of ground-water flow in the Greater Orlando Metropolitan Area, East-Central Florida
A finite-difference ground-water flow model was used to simulate the effects of both modern-day (1988) and projected 2010 ground-water withdrawals on the Floridan aquifer system in the greater Orlando metropolitan area. This area covers about 2,500 square miles and includes all of Orange and Seminole Counties and parts of Lake, Volusia, Brevard, Osceola, and Polk Counties. The hydrogeology of
Authors
L. C. Murray, K. J. Halford
Analysis of ground-water flow in the Catahoula aquifer system in the vicinity of Laurel and Hattiesburg, Mississippi
The upper, middle, and lower Catahoula aquifers in the vicinity of the cites of Laurel and Hattiesburg in southern Mississippi are made up of irregular, discontinuous sand zones in the Catahoula Formation of Miocene age. In places thee three aquifers may be hydraulically well connected, and are referred to as the Catahoula aquifer system. Withdrawal from the Catahoula aquifers increased from 28 mi
Authors
K. J. Halford, N. L. Barber
Potentiometric surface of the upper Floridan Aquifer in the St. Johns River Water Management District and vicinity, Florida, May 1994
This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for May 1994. The map is based on water-level measurements made at approximately 1,000 wells and several springs. Data on the map were contoured using 5-foot contour intervals in most areas. The potentiometric surface of this karstic aquifer generally reflects lan
Authors
D. M. Schiffer, A. M. O'Reilly, G. G. Phelps, L. A. Bradner, K. J. Halford, R. M. Spechler