The monitoring programme Cyclically low-intensity monitored lakes is part of the Freshwater programme of the Swedish Agency for Marine and Water Management (Havs- och vattenmyndigheten), within the national environmental monitoring.
The investigations cover a national scope and the low-intensity monitored lakes are selected to be representative of a variety of lake types over a large area. Moreover, the cyclically low-intensity monitored lakes are to complement the Trend lakes through their larger areal coverage, while the trend lakes primarily monitor changes over time.
The purpose of the cyclical sampling is to
- enable the national environmental objectives to be met
- provide a basis for controlling monitoring according to the Water Administration (Vattenförvaltningen)
- meet international demands on data reporting
- provide a basis for development of assessment criteria
- constitute the basis for official statistics, and give an annual picture of the environmental state of Swedish lakes.
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.