The main purpose of the association is to develop and operate storage reservoirs and regulation systems to level the natural flow of water in the rivers so that the production of electricity can be better adapted to the actual demand. GLB is responsible for 26 reservoirs and watercourse diversions with a combined storage capacity of an approximate 3,500 million m3, equivalent to 16 % of the runoff from the catchments' area during an average year. The licences for the 26 regulating dams and watercourse diversions involved are held by GLB on behalf of the members who are private and publicly owned hydropower companies.
GLB consists of, and is owned by, a total of 21 industrial enterprises and hydroelectric power companies who have 47 power stations within the catchments' area. The annual production by the member hydroelectric power stations will in a good year exceed 10,000 million kilowatt-hours (10 Terawatt-hours), approximately 9 % of Norway's total electricity production.