Lake Geneva is superb, the quality of its water delights the more than 900,000 people who drink it, and bathing is a popular pastime. But this immaculate beauty is not a reflection of Lake Geneva as it was in the past. And yes, 𝗶𝗹 𝗳𝘂𝘁 𝘂𝗻 𝘁𝗲𝗺𝗽𝘀 𝗼𝘂̀ 𝘀𝗲 𝗯𝗮𝗶𝗴𝗻𝗲𝗿 𝗱𝗮𝗻𝘀 𝗹𝗲 𝗹𝗮𝗰 𝗲́𝘁𝗮𝗶𝘁 𝗱𝗮𝗻𝗴𝗲𝗿𝗲𝘂𝘅. But what made it such a hostile environment in the 1960s to 1980s?
Victim of an unprecedented 𝗲𝘂𝘁𝗿𝗼𝗽𝗵𝗶𝘀𝗮𝘁𝗶𝗼𝗻 of its waters, the lake frightened most of the region's inhabitants. The stench was foul, the proliferation of algae and the corpses of dead animals drifting in the currents did not inspire confidence and 𝘀𝗼𝗻 𝗲́𝘁𝗮𝘁 𝘀𝗮𝗻𝗶𝘁𝗮𝗶𝗿𝗲 𝗲́𝘁𝗮𝗶𝘁 𝗰𝗮𝘁𝗮𝘀𝘁𝗿𝗼𝗽𝗵𝗶𝗾𝘂𝗲.
But what is eutrophication?
When nutrients (especially phosphorus) accumulate in an aquatic environment accompanied by an increase in temperature and solar radiation, this encourages 𝗰𝗿𝗼𝗶𝘀𝘀𝗮𝗻𝗰𝗲 𝗱𝗲𝘀 𝗽𝗵𝘆𝘁𝗼𝗽𝗹𝗮𝗻𝗰𝘁𝗼𝗻𝘀 𝗲𝘁 𝗱𝗲𝘀 𝗽𝗹𝗮𝗻𝘁𝗲𝘀 𝗮𝗾𝘂𝗮𝘁𝗶𝗾𝘂𝗲𝘀. High concentrations of these nutrients can lead to rampant growth of these aquatic organisms and 𝗹𝗲𝘂𝗿 𝗱𝗲́𝗰𝗼𝗺𝗽𝗼𝘀𝗶𝘁𝗶𝗼𝗻 𝗰𝗼𝗻𝘀𝗼𝗺𝗺𝗲 𝗲́𝗻𝗼𝗿𝗺𝗲́𝗺𝗲𝗻𝘁 𝗱'𝗼𝘅𝘆𝗴𝗲̀𝗻𝗲. The cycle continues until the available supply of oxygen is exhausted. As a result, the disappearance of the latter leads to 𝗹𝗮 𝗺𝗼𝗿𝘁 𝗱'𝘂𝗻𝗲 𝗽𝗮𝗿𝘁𝗶𝗲 𝗱𝗲 𝗹𝗮 𝗯𝗶𝗼𝗱𝗶𝘃𝗲𝗿𝘀𝗶𝘁𝗲́ 𝗱𝘂 𝗺𝗶𝗹𝗶𝗲𝘂, 𝗽𝗮𝗿 𝗮𝘀𝗽𝗵𝘆𝘅𝗶𝗲. In addition, increased water turbidity can also encourage the growth of potentially dangerous bacteria.
𝗟'𝗲𝘅𝗽𝗹𝗼𝘀𝗶𝗼𝗻 𝗱𝗲́𝗺𝗼𝗴𝗿𝗮𝗽𝗵𝗶𝗾𝘂𝗲 𝗱𝗲 𝟭𝟵𝟱𝟳 𝗮̀ 𝟭𝟵𝟳𝟳 and the development of fertilisers for agriculture and the use of phosphate detergents were the main causes of the asphyxiation suffered by Lake Geneva during this period. fertilisers for agriculture and the use of phosphate-based detergents were the main causes of the asphyxiation suffered by Lake Geneva during this period. During this period, the concentration of phosphorus increased 9-fold! As the few existing wastewater treatment plants were not always adapted to the volume of water to be treated, most of the polluted water was discharged into the lake, 𝘀𝗮𝗻𝘀 𝗮𝘂𝗰𝘂𝗻 𝘁𝗿𝗮𝗶𝘁𝗲𝗺𝗲𝗻𝘁 𝗽𝗿𝗲́𝗮𝗹𝗮𝗯𝗹𝗲. As a result, many places were not recommended for bathing, or even forbidden!
After much effort and several long-running battles by stakeholders all around the lake (including the ASL), 𝗹𝗲 𝗟𝗲́𝗺𝗮𝗻 𝗮 𝗿𝗲𝘁𝗿𝗼𝘂𝘃𝗲́ 𝗽𝗮𝗿𝘁𝗶𝗲𝗹𝗹𝗲𝗺𝗲𝗻𝘁 𝘀𝗼𝗻 𝗼𝘅𝘆𝗴𝗲̀𝗻𝗲, 𝘁𝗼𝘂𝘁 𝗲𝗻 𝗿𝗲𝘀𝘁𝗮𝗻𝘁 𝗰𝗼𝗻𝘃𝗮𝗹𝗲𝘀𝗰𝗲𝗻𝘁. So let's take a dip in it, without forgetting that it wasn't always possible!
Photo: Musée du Léman
𝐒𝐨𝐮𝐫𝐜𝐞𝐬 :
- Lake Geneva n°6 "Lake Geneva is suffocating
- The RTS archives1964 "Lakes in danger
