Compared with other European countries, Norway has a broad and versatile range of relatively intact hydrometric areas. The extent of the activities that influences the hydrometric areas has however increased. Physical interventions, pollution from agriculture, built-up areas or industry are examples of such activities. The climatic changes are also influencing the Norwegian rivers. The Administrative Authority in Norway aims at having a good aquatic environment. This must be documented by surveillance. The Environmental Protection Authorities also requires comprehensive knowledge about processes related to nutritive substances and environmental poisons in Norwegian rivers, in order to assess how the rivers influence the Norwegian coastal areas, and if measures must be implemented for achieving the goal for a healthy aquatic environment.