The heart of the Tuusula municipality and the town of Järvenpää is Lake Tuusulanjärvi, one of the most extensively studied lakes in Finland. The intensive restoration measures were started in 1998 and have continued thereafter. 

The goal of the biomanipulation is both to restrict the growth of cyanobacteria and to make the lake more attractive to recreational fishing.

The basis of permanent improvement of water quality of lake is a sufficient reduction in the external loading from diffuse sources. It consists of leaching from agricultural areas, untreated sewage of scattered settlements and stormwater from densely populated areas.