The Aeration of the Lake begins in 1970’s
Lake Tuusulanjärvi Water Protection Assosiation was founded in 1965 and it started to take action to save the lake in the early 1970s. As the oxygen level of the lake seemed to get worse some aerators were purchased and they started operating early winter in 1972. They operated all winter and were powerful enough to keep the oxygen level satisfactory. Since then, the aerators have been operating every winter and the resuscitation still continues to be necessary.
Aeration is important especially for the water layers near the bottom of the lake: if the level of oxygen decreased the phosporus in the bottom silt starts to be released in the water and consequently enhance the algae production. The oxygen provided by aeration prevents this process.
The next big step on the lake’s path to recovery came in 1979, when the sea sewage that carried wastewaters from the town of Järvenpää to Helsinki to be treated was completed. It was funded by The Mid-Uusimaa Joint Municipal Board for Water Pollution Control. The largest source of nutrient loading of the lake was thus removed. Now only the non-point loading of the lake remained; the nutrients carried by streams and drains and brought on by run-off from agricultural land and wastewaters from households that remained without municipal sewage disposal.
The phosphorus loading of the lake in the late 1970s was nearly 10 tons, but dropped to half with the sea sewage. However, the nutrient loading of the lake was still two times bigger than the lake could bear. The worst was now over but the lake still remained hypertrophic.
The Efficient restoration of the Lake was started in 1998
After an extremely dense bloom of cyanobacteria in 1997, voluntary organization of ProTuusulajärvi was founded and with the help of other organizations it collected 8 643 names in a petition of citizens for the lake’s restoration. Many well-known artists, including writers Veikko Meri and Laila Hietamies, also joined in the public petition, and also high-profile members of society and business life were worried about the condition of the lake.
The petition was handed to The Minister for the Environment, Pekka Haavisto, on the 2nd of October in 1998. As a greeting from the government authorities The Minister gave a promise of 2 million marks’ funding (about 335 000 euros) for the restoration of the L. Tuusulanjärvi. On the same day the municipalities of Tuusula and Järvenpää together with The Mid-Uusimaa Joint Municipal Board for Water Pollution Control agreed to a joint budget of 18.1 million marks (more than 3 million euros) for the restoration of the lake.
Both the state and the municipalities have continued the funding of the restoration since then. The main responsibility of the funding of the lake restoration project remains on municipalities of Tuusula and Järvenpää. The annual budget in 2010’s is about 200 000 euros.
The measures of the restoration are agreed yearly on in steering and working groups which are made up of the representatives of the authorities and interest groups.