R. Allan Freeze

The worth of data in predicting aquitard continuity in hydrogeological design

A Bayesian decision framework is developed for addressing questions of hydrogeological data worth associated with engineering design at sites in heterogeneous geological environments. The specific case investigated is one of remedial contaminant containment in an aquifer underlain by an aquitard of uncertain continuity. The framework is used to evaluate the worth of hard and soft data in investigating the aquitards continuity. The analysis consists of four modules: (1) an aquitard realization generator based on indicator kriging, (2) a procedure for the Bayesian updating of the uncertainty with respect to aquitard windows, (3) a Monte Carlo simulation model for advective contaminant transport, and (4) an economic decision model. A sensitivity analysis for a generic design example involving a design decision between a no-action alternative and a containment alternative indicates that the data worth of a single borehole providing a hard point datum was more sensitive to economic parameters than to hydrogeological or geostatistical parameters. For this case, data worth is very sensitive to the projected cost of containment, the discount rate, and the estimated cost of failure. When it comes to hydrogeological parameters, such as the representative hydraulic conductivity of the aquitard or underlying aquifer, the sensitivity analysis indicates that it is more important to know whether the field value is above or below some threshold value than it is to know its actual numerical value. A good conceptual understanding of the site geology is important in estimating prior uncertainties. The framework was applied in a retrospective fashion to the design of a remediation program for soil contaminated by radioactive waste disposal at the Savannah River site in South Carolina. The cost-effectiveness of different patterns of boreholes was studied. A contour map is presented for the net expected value of sample information (EVSI) for a single borehole. The net EVSI of patterns of precise point measurements is also compared to that of an imprecise seismic survey.

Predictive Simulation of the Subsidence of Venice

Land subsidence at Venice is the result of sediment compaction in the unconsolidated, aquifer-aquitard system that underlies the Venetian Lagoon. Compaction is caused by extensive groundwater withdrawals at the nearby industrial port of Marghera. The total subsidence at Venice for the period from 1930 through 1973 has been about 15 centimeters. Predictive simulations with a calibrated mathematical model were hampered by the sparseness of available data, but, as a first estimate, they suggest that, if withdrawals are kept constant in the future as they have been since 1969, about 3 centimeters of further subsidence can be expected.

Mathematical modeling of solute transport in the subsurface

The quantification of solute transport in the subsurface has become widespread in recent years. Superfund legislation, along with rapid advancement of mini‐ and microcomputer technology, have combined to promote the development of solute transport models. Software has progressed to where practicing scientists and engineers routinely use transport codes, whereas a few years ago, these codes were used predominantly as research tools. Today in the research community, solute transport codes have advanced beyond advection‐dispersion considerations. Thermo‐hydro‐mechanical‐coupled processes can be treated in numerical codes. Statistical approaches are now employed to deal with uncertainty associated with parameters. Techniques are evolving to model transport through low permeability media, taking discrete fractures into account. This review examines current practical applications, parameter uncertainty, and research trends in solute transport quantification in the subsurface.

Advances in the assessment of data worth for engineering decision analysis in groundwater contamination problems.

This article lays out a framework for the evaluation of hydrogeological data worth at waste-management facilities that are potential point sources of groundwater contamination. The framework is developed as a part of the engineering design process; it is based on the premise that hydrogeological data have worth only if the knowledge gained can aid in making decisions between alternative courses of action. The methodology is applicable during the siting process, during facility design, and during assessment of remedial alternatives. It involves the integration of: (1) risk-cost-benefit analysis, (2) a geostatistical description of the hydrogeological parameters, (3) Monte Carlo stochastic simulation, (4) sensitivity analysis, (5) variance reduction, (6) Bayesian updating, and (7) economic regret.

Paul A. Witherspoon (1919–2012)

The hydrologic community lost one of its most charismatic leaders with the death of Paul Witherspoon on 10 February 2012, in Berkeley, Calif. He passed away from complications brought on by his long battle with Parkinsons disease. He was 93. Paul was a dynamic and influential research leader in hydrogeology for more than 50 years. Working from his base at the University of California, Berkeley (UC Berkeley), and later from the Lawrence Berkeley National Laboratory (LBNL), he made significant contributions to the understanding of the flow of fluids in porous media and fractured rock, and he applied his findings to a diverse set of societally important issues, including the development of geothermal energy, use of underground gas storage, and siting and design of nuclear waste disposal facilities. In all these spheres of interest he emphasized the need to marry theoretical studies and field testing. He was especially passionate about the need for large-scale, in situ, underground experiments to guide and corroborate the predictions of theoretically based numerical models.

Groundwater control at Highland Valley Copper

ABSTRACT Groundwater control is a very important component of mining operations at Highland Valley Copper. This paper presents an overview of ongoing engineering studies that are being carried out at Highland Valley Copper to identify the most effective overburden dewatering strategy, a strategy that must result in stable pit walls and a profitable mining operation. The studies are in progress on four fronts. Foremost, this paper reports on the geologic investigations that have been completed in order to develop a geologic model, the basic building block of other focused geotechnical investigations. Second, interpretation of pump test data with the assistance of a state of the art software package is helping to unravel the hydrologic parameters that control groundwater flow in the overburden. Third, maintenance of the existing dewatering system at optimal performance levels is also a very high priority, achieved by groundwater technicians who monitor the dewatering system around the clock. They rely on a ...

Past President's Report: The State of the Section

I would like to take this opportunity to summarize the state of the Hydrology Section of AGU as I see it after 4 years in the trenches (2 as President-Elect and 2 as President). The picture I will paint is a relatively rosy one. I believe the section is healthy and performing its primary functions well with respect to publications, meeting, and awards. The section has also been involved in some special programs and issues that may be of interest to you. In this brief report, I will try to hit the highlighh in each of these areas, closing with mention of the minor but nagging ongoing problems that in my opinion arise largely from a need to grapple with the dichotomies of our section.

Report from Hydrology Section President

The response to the Hydrology Section questionnaire that appeared in Eos earlier this fall (September 11, 1984, p. 690) was very gratifying. More than 100 members took the time to send in a completed copy. There were few harsh complaints but lots of constructive suggestions. Many people volunteered to play an increased role in AGU activities. More than 50 topics were suggested as possible subjects for technical sessions at annual meetings or for Chapman conferences. A summary list of these topics has been sent to each of the technical committee chairmen and to the program chairman for the Spring and Fall Meetings.

AGU hydrology publication outlets

In recent months I have been approached on several occasions by members of the hydrology community who asked me which of the various AGU journals and publishing outlets would be most suitable for a particular paper or article that they have prepared. Water Resources Research (WRR) is the primary AGU outlet for research papers in hydrology. It is an interdisciplinary journal that integrates research in the social and natural sciences of water. The editors of WRR invite original contributions in the physical, chemical and biological sciences and also in the social and policy sciences, including economics, systems analysis, sociology, and law. The editor for the physical sciences side of the journal is Donald R. Nielson, LAWR Veihmeyer Hall, University of California Davis, Davis, CA 95616. The editor for the policy sciences side of the journal is Ronald G. Cummings, Department of Economics, University of New Mexico, Albuquerque, NM 87131

From the incoming President of the Hydrology Section

On July 1 I began my duties as president of the Hydrology Section of AGU. I took over a healthy Section, recognized as the leading scientific society in the field of hydrology. I also am taking over a Section whose position within AGU is strong and influential. These two facts are a tribute to my predecessors, Peter Eagleson and J im Wallis. They have shepherded the Hydrology Section through an important period of technical and political growth, I will try to maintain the pace. During my tenure as president I intend to use our new WaterWatch column as a means of communication with the membership. I hope to keep you informed on the technical and administrative issues that arise and also to use this forum to solicit your views on directions that you would like to see us take. As a first attempt at this type of interaction, I have prepared a questionaire, which appears below. If you have suggestions for technical sessions or Chapman Conferences, if you have views on the various AGU publication programs, or if you can suggest candidates for AGU awards, I urge you to fill out the questionaire and return it to me.