Numerical methods provide a powerful and essential tool for the solution of problems of water resources. This book gives an elementary introduction to the various methods in current use and demonstrates that different methods work well in different situations and some problems require combinations of methods. It is essential to know something of all of them in order to make a reasoned judgement of current practice. Their applications are discussed and more specialised versions are outlined along with many references making this an invaluable, comprehensive coverage of the field.