Model Validation - Perspectives in Hydrological Science
Edited by Malcolm G. Anderson & Paul D. Bates. Published by John Wiley & Sons Ltd, Baffins Lane, Chichester, West Sussex PO19 1UD, UK: 2001: ISBN 0-471-98572-4: 250 ´ 172mm: xi + 500pp: Hardback: £100.
Model validation is a fundamental issue in modern hydrological sciences. New and evolving environmental legislation and regulation have increased the need for predictions and to understand complex relationships. This meant that more modelling is now carried out, made possible by advances in numerical modelling methods and the computer hardware on which to run it.
The book has a broad scope covering elements in the hydrological cycle is broad ranging from the rainfall-runoff relationship and hydraulic models through soil water, snow, and ice-sheets to groundwater and sediment transport. Each of the 18 chapters is written by academic experts in their own fields, which means that each chapter has a slightly different approach to the subject of model validation. There are a total of 30 contributors, 16 from UK universities, three from other EU countries, eight from the USA and three others.
In addition to scientists, philosophers have written chapters on the problems of uncertainty and legal experts on the use of these methods in litigation. Chapter 5 for example, provides an interesting discussion of the use of hydrological models in court cases and what constitutes an acceptable level of proof in these areas.
I was somewhat disappointed however, over the chapter on groundwater modelling. Hydrogeological investigations consist of an iterative process of developing a conceptual understanding of the geological and hydrological relationships that control groundwater flow and limit the availability of recharge. Computer-based models provide a very important tool in this process that allows the significance of individual parts of these relationships to be tested. This process involves both establishing that certain physical processes are significant in a groundwater flow system such as vertical leakage, and sensitivity analysis where the significance of different assumed values of chosen parameters is tested and compared with field data. This approach is essential to select the best value for those aquifer properties that cannot be effectively measured in the field.
It is regrettable that this chapter has been written solely from an American point of view. No one would belittle the contribution that workers in the USA have made to hydrogeological modelling, after all the MODFLOW code - the most widely used groundwater flow model in the world - was originally produced by the US Geological Survey. It is disappointing however, to find that there is scant mention of non-American authors in the list of references cited, with notable omissions including Jacob Bear and Ken Rushton both of whom have made invaluable contributions to groundwater modelling from an international perspective.
Overall, this book is very much one for the academic specialist working in hydrology and unlikely to attract the casual reader. However, it will stimulate thought and further debate within a community including third-year undergraduate and post-graduate students specialising in hydrology as well as those with a career researching this field.
This review appeared in the Journal of the Chartered Institution of Water and Environmental Management 2002, Volume 16, No 4, page 300.
Copyright © CIWEM 2002