How Annecy’s Lake got so pure

Leo writes*

Annecy is a city in eastern France whose lake and vibrant colours attract tourists from all around the country. Boasting a modest population of around 120 000 people, Annecy is a small city with seemingly not many problems in regard to water (Wikipedia). The main attraction is its lake “Lac d’ Annecy.” Often called the blue lung of the region, Lac d’ Annecy helps with droughts and other water issues (Annecy Lake saves local ski station from drought).

This has not always been the case, as the lake’s water was not always so clean. In the last century, the lake was overwhelmed with water demand from growth in development and population (Barraqué, 1986).

When the lake’s water was initially used in 1908, water quality was good enough to forego treatment (Barraqué, 1986). But quality started to deteriorate in the “entre-deux-guerres” (interbellum) period (Barraqué, 1986), as waste waters were discharged into the lake (Le Dauphine). Numerous carnivorous fish species started to disappear — notably the famous Omble chevalier.

After the liberation of France in 1945, growing industry and tourism increased water demand as well as pollution (Barraqué, 1986).

It was only ten years later that the alarm was rung in face of the dire situation. Charles Bosson the maire of Annecy at the time, expedited the complete renovations of sewer systems and water treatment for all municipalities around the lake (Barraqué, 1986). A new syndicate was created in order to address water quality, the SILA (Intercommunal Syndicate of Annecy Lake) which still exists to this day (Le Dauphine).

A completely new system was designed: a collection belt around the lake brought waste water to Annecy for treatment. This solution, although more costly for Annecy spread the costs and benefits of the new system between the communes of the lake. For the scale of the town at the time, this construction was massive: 47km of collection pipes, 190 km of new sewer pipes and a new purification facility (Barraqué, 1986). All for 2,275 billion French francs or the equivalent of 350 million euros today (Le Dauphine). With the system’s completion in 1976, water quality improved (Le Dauphine). Today, Lake Annecy has a reputation as the purest and cleanest lake in Europe.

Bottom Line: The modernisation of Annecy’s water management systems permitted its transition from a polluted body of water to one of Europe’s purest lakes.

* Please help my Water Scarcity students by commenting on unclear analysis, alternative perspectives, better data sources, or maybe just saying something nice 🙂

Author: David Zetland

I'm a political-economist from California who now lives in Amsterdam.

3 thoughts on “How Annecy’s Lake got so pure”

  1. Hi Leo,
    It was fascinating to learn that a lake as beautiful and pure as this one had a dark past. It gives hope to other polluted lakes. However, with the region’s increasing popularity, not only for tourists but also for living, I wonder how they will maintain the high water standards. As the activity in the area increases, we may expect the lake to become more polluted and more water to be used from it. Does the SILA plan to expand its system if it becomes overused, or is there still a significant margin before this happens?

    1. Thanks for your comment Bodil. I agree that the story is good example of a sucessful lake cleaning operation, the story and the lake’s reputation even attracted foreign interest from China, who adopted lake annecy’s model for one of their lakes ( In regards to water quality, SILA have an extremely rigorous program to keep the lake’s water pure. SILA collaborates with the french national agronomic institute and have put in place scientific monitoring of the lake. For this reason, i do not think the lake will become more polluted in the forseeable future, even with population and touristic increase. Any littering in or around the lake is severly frowned upon by locals as there is a high communal respect for the lake.
      When it comes to supply though, you pose an important question. The lake most summers goes down significantly, sometimes more than a meter. Summer droughts are the cause of this, and they seem to be getting worse year by year. The current strategy put in place is this: communes without direct access have to be able to rely on an alternative water source if the situation requires it. As the lake in summer serves often as a safety solution, it was voted that the reduction of water carrying trucks taking water from the lake was the first priority.

Leave a Reply

Your email address will not be published. Required fields are marked *