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Advective transport in a multilayered system of aquifers
4A sampling wells, the other for when there are data from only one well. No a priori knowledge of direction or magnitude of pore velocity is required. Example calculations are shown. 941022 Extension of the method of characteristics for simulation of solute transport in three dimensions Zheng, C Ground Water 1/31, N3, May-June 1993, P456-465 Modifications are proposed to the traditional method of characteristics approach for analysis of 3D solute transport. They enable computer memory and processing time requirements to be reduced and can also provide improved mass balance results. The accuracy of the modified procedure is illustrated by comparisons of its output with analytical solutions for 3D advection and dispersion in a spherical flow field and concentration change in a well during an injection/pumping cycle. 941023 Simulation of cylindrical flow to a well using the U.S. Geological Survey modular fiuite-differeoce ground-water flow model. Computer note Reilly, T E; Harbaugh, A W Ground Water 1/31, N3, May-June 1993, P489-494 The USGS modular 3D finite difference groundwater flow model has been modified to simulate axisymmetric flow to a well, an important topic in groundwater hydraulics. The theory includes the concept of concentric shells capable of reproducing large variations in gradient in the vicinity of the well by decrease in their area in the direction of the well. A computer program which acts as a preprocessor to the USGS model and creates the input data file is presented. Model output is compared to that from analytical solutions. 941024 Flow between aquifers through filled cylindrical conduits: analytical solution and application to underground nuclear testing sites Brikowski, T J Hydrol V146, N1/4, June 1993, Pl15-130 Simple solutions are obtained for groundwater flow in filled cylindrical conduits connecting multiple aquifers. Both confined and unconfined upper aquifer systems are examined. Conduit flux will depend on bulk transmissivity of the conduit-aquifer system and will be large only when there is little variation from this average throughout the system. Application to a hypothetical nuclear test site with a vertical rubblefilled chimney indicates conduit flow is approximately equivalent to that allowed by an unsealed borehole of diameter 0.3m. 941025 Advective transport in a multilayered system of aquifers Verruijt, A; Swidzinski, W Trans Porous Media V12, N1, July 1993, P31-42 A three dimensional model is presented for transport in a porous medium comprising of a system of aquifers and aquitards. The Dupuit assumption that vertical gradient of the hydraulic head can be neglected with respect to horizontal gradient is maintained. Transport of pollutants is limited to advective transport and linear adsorption. The governing equations are formulated and solved using a finite element technique.
941026 Implementation of electromagnetic method to delineate shallow aquifers Alwail, T A; Stewart, M T Proc 29th Symposium on Engineering Geology and Geoteehnical Engineering, Reno, 22-24 March 1993 P90-105. Publ Reno: University of Nevada, 1993 The Pliocene reefal limestones of western Collier County, Florida, are an important source of potable water. An integrated geologic, hydrologic, and geophysical survey has been carried out to delineate relations between lithofacies, hydrogeological properties, and geophysical signatures. Outcrop, borehole, and canal dredge spoil bank rocks were examined. Electromagnetic terrain mapping, fluid conductivity measurements at surface water sites, and analyses of well water were carried out. Two zones were delineated, active flow/low conductivity and stagnant flow/high conductivity. Correlations with rock characteristics and implications to groundwater quality are discussed.
Chemical and physical changes due to water See a~o." 941010, 941133 941027 Preconstruction solution for groundwater rise in sabkha Shetata, W; Lofti, H int Assoe Engng Geol Bull N47, April 1993, P145-150 Groundwater rise in Gulf Coast sabkha, the most prominent cause of which is impedance of natural evaporation by construction, can lead to settlement of surface structures. Potential groundwater rise has been assessed using evaporation and soil porosity data. Horizontal drains are proposed to prevent the rise in water table. A simple mathematical model is presented to optimise drainage design for given site conditions and drain characteristics. 941028 Acidic mine drainage in carbonate terrains: geochemical processes and rates of calcite dissolution Wicks, C M; Groves C G J tlydrol 1/146, N1/4, June 1993, P13-27 Rates of calcite dissolution were determined from weight loss data for Iceland Spar single crystals suspended in an East Tennessee stream affected by acid mine drainage, pH ranged from 3.6-7.7. Rates were much lower than predicted by the Plummer et al (1978) dissolution rate law and those measured in laboratory acidic waters. Inhibition of dissolution by iron and possibly other solutes in the stream water is suggested as a possible explanation. 941029 Geochemistry of the Obey River Basin, north-central Tennessee: a case of acid mine water in a karst drainage system Sasowsky, I D; White, W B J Hydrol V146, N1/4, June 1993, P29-48 Many upper basin tributaries of the East Fork of the Obey River are contaminated by acid drainage from coal mines. The lower basin is drained through a deep gorge cut down into Mississippian carbonate rocks. The lower basin is karstic, with a 9km length of the river underdrained by a conduit system. Although these waters are buffered, acidity reduces only slowly, and acidic waters appear at a spring deep in the karst, having survived 5km of travel. Alkalinity increases in the lower reaches of the basin, but most waters remain highly undersaturated with respect to calcite.
941026 Implementation of electromagnetic method to delineate shallow aquifers Alwail, T A; Stewart, M T Proc 29th Symposium on Engineering Geology and Geoteehnical Engineering, Reno, 22-24 March 1993 P90-105. Publ Reno: University of Nevada, 1993 The Pliocene reefal limestones of western Collier County, Florida, are an important source of potable water. An integrated geologic, hydrologic, and geophysical survey has been carried out to delineate relations between lithofacies, hydrogeological properties, and geophysical signatures. Outcrop, borehole, and canal dredge spoil bank rocks were examined. Electromagnetic terrain mapping, fluid conductivity measurements at surface water sites, and analyses of well water were carried out. Two zones were delineated, active flow/low conductivity and stagnant flow/high conductivity. Correlations with rock characteristics and implications to groundwater quality are discussed.
Chemical and physical changes due to water See a~o." 941010, 941133 941027 Preconstruction solution for groundwater rise in sabkha Shetata, W; Lofti, H int Assoe Engng Geol Bull N47, April 1993, P145-150 Groundwater rise in Gulf Coast sabkha, the most prominent cause of which is impedance of natural evaporation by construction, can lead to settlement of surface structures. Potential groundwater rise has been assessed using evaporation and soil porosity data. Horizontal drains are proposed to prevent the rise in water table. A simple mathematical model is presented to optimise drainage design for given site conditions and drain characteristics. 941028 Acidic mine drainage in carbonate terrains: geochemical processes and rates of calcite dissolution Wicks, C M; Groves C G J tlydrol 1/146, N1/4, June 1993, P13-27 Rates of calcite dissolution were determined from weight loss data for Iceland Spar single crystals suspended in an East Tennessee stream affected by acid mine drainage, pH ranged from 3.6-7.7. Rates were much lower than predicted by the Plummer et al (1978) dissolution rate law and those measured in laboratory acidic waters. Inhibition of dissolution by iron and possibly other solutes in the stream water is suggested as a possible explanation. 941029 Geochemistry of the Obey River Basin, north-central Tennessee: a case of acid mine water in a karst drainage system Sasowsky, I D; White, W B J Hydrol V146, N1/4, June 1993, P29-48 Many upper basin tributaries of the East Fork of the Obey River are contaminated by acid drainage from coal mines. The lower basin is drained through a deep gorge cut down into Mississippian carbonate rocks. The lower basin is karstic, with a 9km length of the river underdrained by a conduit system. Although these waters are buffered, acidity reduces only slowly, and acidic waters appear at a spring deep in the karst, having survived 5km of travel. Alkalinity increases in the lower reaches of the basin, but most waters remain highly undersaturated with respect to calcite.