Conventional pump-and-treat technologies are among the most widely used systems for the remediation of contaminated ground water. Within recent years it has become recognized that these systems can require protracted periods of time to make significant reductions in the quantity of contaminants associated with both the liquid and solid phases which constitute the subsurface matrix. Evaluating t...

The calculation of ground water transit times is one important factor in ground water protection. In this paper, we present an analytical solution for the transit time for a Dupuit-type flow system applicable to saturated flow through a horizontal leaky aquifer discharging to a downgradient fixed-head boundary under steady-state conditions. We investigate the influence of leakage when comparing...

Water Howellia (Howellia aquatilis) is a rare and endangered wetland plant listed as a threatened species under the Federal Endangered Species Act. 70% of the world population is found in the 1:7 £ 10 ha Swan Valley, Montana, USA in wetlands of usually less than 1-ha. Survival of this aquatic species requires emergence during mid-summer, the drying out of occupied portions of the wetlands, a sl...

IGW is a software environment for real-time 2D and 3D groundwater modeling. The software functions as a ‘‘numerical laboratory’’ in which the modeler can freely explore: visually creating an aquifer of desired configurations and then immediately investigating and visualizing the groundwater system. IGW allows the modeler’s thought processes to progress naturally and intuitively with the informa...

Idealized laboratory experiments reported in the literature have been designed to simulate specific physical and chemical conditions. These laboratory conditions have allowed researchers to control the variables which affect the behavior of contaminants in the subsurface and to identify the mechanisms which are likely to occur in the field. An understanding of the various mechanisms of facilita...

Introduction The development and application of ground-water models has been an important component of USGS hydrologic investigations since the early 1970s. During the past 35 years, the USGS has developed a wide range of computer models to simulate saturated and unsaturated subsurface flow, solute transport, and chemical reactions. The most widely used of these programs is the MODFLOW model, w...