The Workshop on Parameter Identification and Inverse Problems in Hydrology, Geology and Ecology, Karlsruhe, April 10-12, 1995, was organized to bring to­ gether an interdisciplinary group drawn from the areas of science, engineering and mathematics for the following purposes: - to promote, encourage and influence more understanding and cooperation in the community of parameter identifiers from various disciplines, - to forge unity in diversity by bringing together a variety of disciplines that attempt to understand the reconstruction of inner model parameters, un­ known nonlinear constitutive relations, heterogeneous structures inside of geological objects, sources or sinks from observational data, - to discuss modern regularization tools for handling improperly posed pro­ blems and strategies of incorporating a priori knowledge from the applied problem into the model and its treatment. These proceedings contain some of the results of the workshop, representing a bal­ anced selection of contributions from the various groups of participants. The reviewed invited and contributed articles are grouped according to the broad headings of hydrology, non-linear diffusion and soil physics, geophysical methods, mathematical analysis of inverse and ill-posed problems and parallel algorithms for inverse problems. Some of the issues adressed by the articles in these proceedings include the rela­ tion between least squares and direct formulations of inverse problems for partial differential equations, nonlinear regularization, identification of nonlinear consti­ tutive relations, fast parallel algorithms for large scale inverse problems, reduction of model structures, geostatistical inversion techniques.

Table of Contents:
Tutorial on Inverse Problems.- 1. An Introduction to Inverse Problems in Partial Differential Equations for Physicists, Scientists and Engineers.- Hydrology.- 2. Interpretation of Field Tests in Low Permeability Fractured Media. Recent Experiences.- 3. New Front Limitation Algorithm.- 4. Identification and Reduction of Model Structure for Modeling Distributed Parameter Systems.- 5. Results from a Comparison of Geostatistical Inverse Techniques for Groundwater Flow.- Nonlinear Diffusion and Soil Physics.- 6. Identification of the Hydraulic Diffusivity of a Soil by Inverse Method with Dual-Energy Gamma Ray Attenuation Measurements.- 7. Identification of Parameters for Heat Conductivity Equations.- 8. Sensitivity Analysis in Parameter Identification, Test Planning and Test Evaluation Procedures for Two-Phase Flow in Porous Media.- 9. An Inverse Problem for Porous Medium Equation.- 10. Evaluation of Different Boundary Conditions for Independent Determination of Hydraulic Parameters Using Outflow Methods.- Geophysical Methods.- 11. Gravity Data Inversion Using Subspace Method.- 12. A Method to Determine Parameters of a Linear Functional Equations Set and its Application to the Lightning Location Problem.- Mathematical Analysis of Inverse and Ill-Posed Problems.- 13. Stability Estimates for Inverse Problems.- 14. Identifiability of Distributed Physical Parameters.- 15. Inverse Scattering Problem for the Wave Equations and its Applications.- 16. A Descriptive Regularization Approach for a Class of Ill-Posed Nonlinear Integral Equations.- 17. Parameter Estimation in Nonlinear Models by Using Total Least Squares.- 18. Tikhonov Regularization for Identification Problems in Differential Equations.- Parallel Algorithms for Inverse Problems.- 19. Parameter Estimation in MultispeciesTransport Reaction Systems Using Parallel Algorithms.- 20. On Design and Implementation of Parallel Algorithms for Solving Inverse Problems.