Robert Holmes, Jr., Ph.D., P.E., F.ASCE, F.EWRI, D.WRE (Former Employee)

Desbarats [1990] used a particle-tracking scheme to investigate the physics of three-dimensional solute transport in aquifers composed of two porous media of different hydraulic conductivities. The spatially heterogeneous fluid velocity was assumed to be the only mechanism of solute movement; local or pore scale dispersion and molecular diffusion were assumed to be negligible. The...

A new three-dimensional model of solute transport in groundwater that is based on a widely used two-dimensional method of characteristics model and is coupled to a modular finite-difference flow model is under development. The model's accuracy for ideal aquifers having homogeneous properties, uniform boundary conditions, and steady flow along a grid direction is demonstrated by...

This paper investigates the effects of transient groundwater flow on dispersion of a waste chloride plume in the basaltic aquifer beneath the Idaho (USA) National Engineering Laboratory. In an early application of numerical modeling techniques to the two-dimensional simulation of field-scale plumes, previous investigators identified longitudinal and transverse dispersivities using an...

Joint research by the U.S. Geological Survey and the University of Missouri-Rolla currently (1990) is being conducted on a 3.05 meters in diameter vertically rotating flume used to simulate mudflows under steady-state conditions. Observed mudflow simulations indicate flow patterns in the flume are similar to those occurring in natural mudflows. Variables such as mean and surface velocity...

A block-centered, finite difference model of two-dimensional groundwater flow yields velocity values at the midpoints of interfaces between adjacent blocks. Method of characteristics, random walk and particle-tracking models of solute transport require velocities at arbitrary particle locations within the finite difference grid. Particle path lines and travel times are sensitive to the...

This paper investigates the effects of large-scale temporal velocity fluctuations, particularly changes in the direction of flow, on solute spreading in a two-dimensional aquifer. Relations for apparent longitudinal and transverse dispersivity are developed through an analytical solution for dispersion in a fluctuating, quasi-steady uniform flow field, in which storativity is zero. For...

Analytical solutions have been developed for many conceptual models of solute transport in groundwater (Bear 1979). Although these models usually rely on assumptions too restrictive for accurate description of actual field situations, they are useful in understanding groundwater transport and in evaluating the relative importance of the subsurface processes affecting transport. In...

Contaminants from uranium tailings disposed of at an active mill in Colorado have seeped into the shallow ground water onsite. This ground water discharges into the Arkansas River Valley through a superposed stream channel cut in the resistant sandstone ridge at the edge of a synclinal basin. In the river valley, seasonal surface-water irrigation has a significant impact on hydrodynamics...