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MODFLOW-2005 : the U.S. Geological Survey modular ground-water model--the ground-water flow process

The purpose of this survey is to review parameter identification procedures in groundwater hydrology and to examine computational techniques which have been developed to solve the inverse problem. Parameter identification methods are classified under the error criterion used in the formulation of the inverse problem. The problem of ill-posedness in connection with the inverse problem is addressed. Typical inverse solution techniques are highlighted. The review also includes the evaluation of methods used for computing the sensitivity matrix. Statistics which can be used to estimate the parameter uncertainty are outlined. Attempts have been made to compare and contrast representative inverse procedures, and direction for future research is suggested.

Review of Parameter Identification Procedures in Groundwater Hydrology: The Inverse Problem

A review of baseflow recession analysis

Simulation model of the water balance of a cropped soil: SWATRE

The Limburg Soil Erosion Model (LISEM) is a physically based model incorporated in a raster geographical information system. This incorporation facilitates easy application in larger catchments, improves the user-friendliness by avoiding conversion routines and allows the use of remotely sensed data. Processes incorporated in this model are rainfall, interception, surface storage in microdepressions, infiltration and vertical movement of water in the soil, overland flow, channel flow, detachment by rainfall and through-fall, detachment by overland flow and transport capacity of the flow. Special attention has been paid to the influence of tractor wheeling, small roads and surface sealing.

LISEM: a single-event physically based hydrological and soil erosion model for drainage basins; I: theory, input and output

Least squares regression and linear programing for least absolute error estimation are each combined with groundwater solute transport simulation to identify the locations and magnitudes of aquifer pollutant sources. Pollutant sources are identified by matching simulated and measured nonreacting solute concentration data. We have assumed known hydraulic parameters but considered concentration data errors explicitly. The identification models are demonstrated and compared using two hypothetical aquifer systems, one for the steady state case and the other for the transient case. Steady state models identified unknown pipe leak locations and leak magnitudes based upon sparse and spatially distributed chloride and tritium data. The number of likely leak locations was restricted in the models by employing mixed integer programing and stepwise multiple regression. Transient models identified several annual disposal fluxes in the aquifer based upon concentration histories collected at observation wells. In this case, conservative solute concentration data were abundant and contained substantial errors. Minimizing either least absolute or least squared errors was successful in identifying pollutant sources. Furthermore, we demonstrate error analysis for the results given by either method.

Identifying sources of groundwater pollution: An optimization approach

Numerical methods in subsurface hydrology

A mathematical model is developed describing moisture removal from soil by the roots of transpiring plants. The model uses a macroscopic extraction term in the one-dimensional soil moisture flow equation. It describes both moisture removal by the plant and induced moisture movement through the soil. A numerical procedure based on the Douglas-Jones predictor-corrector method is used to solve the model, and solutions are compared with experimental data. The results indicate that extraction term models are computationally and physically feasible and give insight into the mechanics of the overall moisture extraction process.

Extraction term models of soil moisture use by transpiring plants.

This is the first textbook specifically designed for university courses in groundwater modeling. There are books devoted to the exposition of the mechanics of groundwater, to the mathematics of finite differences and finite elements, and to overviews of modeling technology. However, this book leads the student from elementary concepts through the mathematics and modeling procedures and to the solution of problems.

The book is very readable and is aimed at the student whose preparation is limited to elementary calculus. More difficult and peripheral topics such as Anisotropy and Tensors, the Variational Method, Isoparametric Quadrilateral Elements, and Analogies are reserved for appendices.

Introduction to Groundwater Modeling: Finite Difference and Finite Element Methods

The linear programming-superposition method is presented for managing multiple sources of groundwater pollution over time. The method uses any linear solute transport simulation model to generate a unit source-concentration response matrix that is incorporated into a management model. This series of constraints indicates local solute concentration histories that will result from any series of waste injection schedules. The linear program operates on the matrix to arrive at optimal disposal schedules. An example demonstrates application of the method to maximizing groundwater waste disposal while maintaining water quality of local water supplies within desired limits. Flow field variation associated with waste injection are ignored as an approximation. Parametric programming is shown to be an important tool in evaluating waste disposal trade-offs at various injection sites over time. Mixed-integer programming permits restrictions to be placed upon the number of injection wells which may operate during given management periods.

Irwin Remson

Papers

Identifying sources of groundwater pollution: An optimization approach

Numerical methods in subsurface hydrology

Extraction term models of soil moisture use by transpiring plants.

Introduction to Groundwater Modeling: Finite Difference and Finite Element Methods

Optimal dynamic management of groundwater pollutant sources