The programme comprises water sampling for chemical analysis in 800 lakes every year, in a six-year cycle, such that the lakes are sampled once every six years. Thus, a cycle of six years covers in total 4800 lakes. The sampling occurs during the autumn circulation period. The lakes are selected to be representative of the whole area of Sweden.
The lakes are selected through stratified sampling from the lake register of the Swedish Meteorological and Hydrological Institute (SMHI), such that the results may be converted to describing the distribution of environmental states in all lakes of Sweden >0.01 km2
The cyclically monitored lake programme commenced in 2007. Previously, nationally covering lake inventories were made in the so-called National Inventories (Riksinventeringar) approximately every fifth year.
