This monograph represents many years of groundwater data accumulation by a large number of noted hydrogeologists located throughout the world. The project began under the direction of the Russian Academy of Sciences during the time of the USSR. In that context, a substantial part of the descriptive material on hydrogeologic phenomena relies on former USSR examples. By far however, the majority of the material in the book is derived from major continental studies and specific country investigations within those continents. As the English Editor, several points need to be made relative to the document. First, the book represents a multi cultural approach to groundwater resources and their use. As a result, many of the fundamental concepts in hydrogeology are interpreted slightly differently in other countries. In fact, there are a number of hydrogeologic phenomena introduced that for the most part have not been presented internationally. Since various cultures review the science of hydrogeology with their own nuances, a substantial effort was made to provide classic references in the science of hydrogeology. Attempts were not made to show that one country’s approach to a problem was better than another countries cultural approach to the same problem. The focus of the monograph was to present data and scientific principals, which are relevant to groundwater use in each of the countries.