This book presents the Proceedings of the Fourth International Conference ENVIROSOFT 92. Since the beginning of this conference cycle in 1986, EN­ VIROSOFT has provided a forum for discussion and debate for scientists, engineers and decision makers involved in the development and application of computer techniques to environmental sciences. Our main goal is to pro­ vide an opportunity for cross-fertilization among the several groups involved in the study of the environment. A couple of years ago a reviewer of ENVIROSOFT 90 made a very in­ teresting and appropriate comment. He congratulated us for the effort of providing a forum for discussion among environmental scientists but criti­ cized us for maintaining, in the proceedings and in the conference schedule, a strict division between 'atmospheric' papers, 'water' papers, etc. I agree with the reviewer and, in this conference, I made an effort to separate the articles not on the basis of their physical medium (air, water, groundwa­ ter, etc.) but on the basis of the methods and approaches adopted by the authors. Again, I hope that this change will improve the dialogue among scientists and, in particular, the interactions between 'air' and 'water' re­ searchers.