This guide gives comprehensive advice on the designing and setting up of monitoring programmes for the purpose of providing valid data for water quality assessments in all types of freshwater bodies. Designed to provide the essential information to agencies and individuals responsible for water quality, it covers the selection of variables to be measured in water, sediment and biota, concentrating particularly on current water quality issues around the world. In addition, individual chapters describe the special features and water quality problems of rivers, lakes/reservoirs, and groundwater, illustrating different monitoring strategies and techniques with examples. Specific approaches to data handling, treatment, interpretation and presentation are described in the final chapter.