The “réservoir de Montsouris” is one of Paris’ five drinking-water reservoirs. Located in the 14tharrondissement, in the South of the capital, it is its biggest reservoir and can hold up to 203,000 cubic metres of water at full capacity (i.e. approximately the amount drunk by 1/3 of Parisians daily). The reservoir was built between 1869 and 1874 and sits on one of the capital’s highest points, on a site previously occupied by quarries.
The water stocked at the Montsouris reservoir travels via two aqueducts which are built at a slight incline so that no additional electricity or pumping systems are needed to transport the water. Throughout its journey, the water never comes into contact with the air outside and once it has been rendered drinkable, it is kept inside the reservoir where it is shielded from pollution and sunlight.
The reservoir is a truly impressive structure, comprised of two floors and 4 water tanks all supported by 1,800 pillars. Up until 1996, small aquariums built around the tanks called “troutometres” were used to test water quality: trout (yes, the fish) would be released into the water to check whether the water was safe for drinking.
The reservoir can sadly only be observed from the outside as access to it is restricted due to security and hygiene concerns, but the Paris city website will take you on a virtual tour with photos. You can also take a look yourself on your way to the Parc Montsouris (PS : make a little detour through the quaint square Montsouris)!