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J. S. Weiss

Publications and source records attributed to J. S. Weiss.

6 recordsLinked to original sources
USGS2006

Simulation of ground-water flow in a mined watershed in eastern Ohio

A 43-acre watershed in Muskingum County, Ohio, was studied to determine the hydrologic consequences of strip mining for coal. A quantitative description of the effects on the ground-water flow components of the hydrologic system has been obtained using digital models. The premining watershed was characterized by nearly flat-lying sedimentary rocks of the Pennsylvanian System. Underclay beneath the two major coal beds formed bases for perched zones, creating three separate aquifers. Recharge to the ground-water system occurred mainly by percolation of precipitation. Most of the discharge from the top and middle aquifers occurred by downward leakage to the underlying aquifers. A smaller amount of discharge occurred as springflow or streamflow near the intersections of the underclays and land surface. Mining has destroyed the top aquifer, and has replaced the bedrock by spoil material. Water levels in the spoils are at a much lower altitude than existed in the premining top aquifer because of a combination of (1) a larger hydraulic conductivity, (2) areal variations of the hydraulic characteristics of the confining bed, and (3) a slower rate of recharge from precipitation caused by removal of vegetation and soil compaction. Covering of previously exposed portions of the middle aquifer and a lower hydraulic head in the spoils has allowed less recharge to the middle aquifer. Additional flow is induced across the western boundary of the watershed and has reduced the outflow across the eastern boundary. Discharge from the middle aquifer as downward leakage and streamflow is less than before mining.

Groundwater↗
USGS1991

Geohydrologic units of the Mississippi embayment and Texas coastal uplands aquifer systems, south-central United States

As part of the U.S. Geological Survey's Regional Aquifer-System Analysis (RASA) program, the Gulf Coast RASA was initiated to investigate all Tertiary and Quaternary aquifers underlying the Coastal Plain in the south-central United States. Geohydrologic units that make up two of the three regional aquifer systems Mississippi embayment and Texas coastal uplands in the area are described in this report. The gulfward boundary of the outcrop of the two aquifer systems is the southernmost outcrop or subcrop of the Vicksburg-Jackson confining unit, and the updip boundary is the contact between Cretaceous and Tertiary deposits, extending northward to the southern tip of Illinois. The uppermost Cretaceous aquifer, the McNairy-Nacatoch aquifer in the northern part of the Mississippi embayment, is also included where it may be hydraulically connected to the younger sediments. Major regional geohydrologic units generally are coincident with previously defined geologic units. Most of the geohydrologic units consist of alternating sand and clay; however, the entire sequence becomes a clay and carbonate facies gulfward. The regional geohydrologic units delineated in this study, from youngest to oldest, are (1) Mississippi River Valley alluvial aquifer, (2) Vicksburg-Jackson confining unit, (3) upper Claiborne aquifer, (4) middle Claiborne confining unit, (5) middle Claiborne aquifer, (6) lower Claiborne confining unit, (7) lower Claiborne-upper Wilcox aquifer, (8) middle Wilcox aquifer, (9) lower Wilcox aquifer, (10) Midway confining unit, and (11) McNairy-Nacatoch aquifer. The Mississippi embayment aquifer system contains all of these units and has a maximum thickness of about 5,000 feet. The Texas coastal uplands aquifer system, which is contiguous with the Mississippi embayment aquifer system and extends westward and southwestward from the Sabinc uplift, contains all of the foregoing geohydrologic units except the Mississippi River Valley alluvial aquifer, the lower Wilcox aquifer, and the McNairy-Nacatoch aquifer. The Texas coastal uplands aquifer system has a maximum thickness of about 7,000 feet.

Alabama, Arkansas, Illinois, Kentucky, Louisiana, ↗
USGS1990

Geohydrologic units of the coastal lowlands aquifer system, south-central United States

The coastal lowlands aquifer system is one of the three regional aquifer systems studied as part of the Gulf Coast Regional Aquifer-System Analysis (RASA). The coastal lowlands aquifer system underlies about 160,000 square miles of the coastal areas of Texas, Louisiana, Mississippi, Alabama, and westernmost Florida, and nearby offshore areas; the aquifer system is composed of sediments of Oligocene age and younger. The sediments consist predominantly of interbedded sand, silt, and clay with minor amounts of lignite and limestone. The average thickness of the sediments is about 6,000 feet, with a maximum thickness of more than 18,000 feet occurring offshore from southern Louisiana. The base of the coastal lowlands aquifer system is the top of the Vicksburg-Jackson confining unit, which is a massive clay that represents the last major transgression of the sea. A zone of abnormally high fluid pressure (geopressured zone) is present above the top of the Vicksburg-Jackson confining unit onshore in a narrow band along the coast of Texas and Louisiana and on the Continental Shelf. Where the geopressured zone is Present, it is considered to be the base of the coastal lowlands aquifer system. The sediments in the coastal lowlands aquifer system are divided into five Permeable zones and two confining units. The permeable zones are not separated by intervening, regionally mappable confining units in about 64 percent of the study area. In much of the area boundaries between permeable zones were extended, as a constant proportion of the total aquifer system thickness, from areas with hydraulic-head data to areas without such data. Average sand percentage of the permeable zones ranges from about 40 percent to more than 60 percent. However, the areal distribution of sand is variable within and among Permeable zones. A lobate pattern of greater sand percentages is typical of the Permeable zones, and all zones except one have at least one area with sand percentage greater than 80 percent. Data that are useful for quantitative analysis of regional ground-water flow in the coastal lowlands aquifer system are presented in map format. Included for each of the five permeable zones are maps of altitude of the top, thickness, sand percentage, and aggregate thickness of sand. Included for each of the two confining units are maps showing altitude of the top, and thickness of the unit.

Open-File Report↗
USGS1990

Ground-water flow in the Gulf Coast aquifer systems, south central United States — A preliminary analysis

A major objective of the Gulf Coast Regional Aquifer-System Analysis is to use digital models of regional groundwater flow systems to develop better understanding and to improve management of the resource. Modeling is used to synthesize information about the aquifer systems and to test hypotheses about the relative importance of the components of the systems. The 290,000-sq mile study area in the Gulf of Mexico Coastal Plain includes the Mississippi embayment, Gulf Coastal Plain of Texas, and the Continental Shelf that are underlain by deposits of Tertiary and younger age, which contain fresh and saline water. A 10-layer, finite-difference, variable density model, with blocks 10 miles on a side, was used to simulate groundwater flow before development and in 1980, assuming steady- state conditions. Preliminary results indicate that the major factors controlling predevelopment regional flow are the topography, land-surface outcrop pattern, and geometry of aquifers and confining units. Geologic structure and the distribution of precipitation were less significant factors. The density of saline water in the deeper parts of the aquifer system probably has a substantial effect on regional groundwater flow that extends into the freshwater part of the system. Variable water density may be a significant driving force that transports salt great distances in many directions, including updip. The distribution and rates of regional recharge and discharge have been substantially changed by development. Groundwater pumpage in 1980 was about five times the value of predevelopment regional recharge. About 80% of the pumpage was supplied from increased regional recharge. Also resistance to vertical flow caused by many fine-grained beds within the permeable zones can be as important as resistance caused by regional confining units.

Gulf Coast aquifer systems↗
USGS1985

Subdivision of thick sedimentary units into layers for simulation of groundwater flow

Subdividing thick sedimentary units into model layers based solely on stratigraphy can lead to serious violation of groundwater flow modeling restraints and produce erroneous results. Borehole geophysical data can be used to suggest relative permeabilities and delineate model layers that are more likely to have uniform hydraulic properties than layers delineated by stratigraphic definitions alone. The uniformity within layers emphasizes the permeability contrast between layers, thereby allowing a quasi three-dimensional approach. These methods are applied to the thick sedimentary units of the Gulf Coastal Plain, USA.

Groundwater↗