Where does my water come from?

How is our drinking water actually obtained and what path does it take before it comes out of our tap?

Water cycle explained simply

Our drinking water system can be visualized as an endless cycle. Approximately 70% of the Earth's surface is covered with water. The cycle begins with the evaporation of this water, which is found in the seas, lakes, and rivers. This process leads to water storage in the Earth's atmosphere, or in other words, cloud formation. From there, it returns to the Earth's surface in the form of rain, snow, or hail. Once on the ground, the rain or meltwater from the snow seeps into the earth. The water has now reached the groundwater. Waterworks, for example, can then pump this groundwater and, after treatment, feed it into our drinking water network. Finally, our groundwater returns to our oceans through backflow, and the entire cycle can begin again.

Drinking water supply Switzerland

In Switzerland, we obtain our drinking water from various sources, which then reaches us through a widely branched distribution network. Approximately 40% of our drinking water in Switzerland comes from spring water, which is mostly found in the Alps and the Jura Mountains. Another 40% comes from our groundwater reservoirs, which in Switzerland total approximately 50 billion cubic meters. These are mainly located in the Swiss Plateau. The remaining 20% ​​of our drinking water is obtained from lakes, which are vast water reservoirs.

Drinking water extraction from spring water

When extracting drinking water from the spring, rainwater first seeps into the ground. It passes through various soil layers, where it is naturally filtered. Afterward, it flows horizontally along layers of clay or rock. Unlike groundwater, it therefore generally requires no additional treatment. This spring water is then conveyed through a seepage pipe into underground well chambers. There, any sand and other fine particles are filtered out and subsequently stored in a reservoir.

Drinking water extraction from groundwater

Groundwater, on the other hand, is formed when rainwater seeps into impermeable soil layers and collects. From there, it is pumped directly into groundwater reservoirs through well shafts. When the reservoir is full, the groundwater overflows and is fed into our drinking water network.

Treating drinking water

In Switzerland, the quality of tap water is quite good thanks to comprehensive water protection measures. Therefore, one-third of our drinking water can be fed into the drinking water network without treatment. Another third undergoes single-stage filtration with ozone or UV radiation and chlorination. The final third undergoes multi-stage treatment. Our drinking water can be treated in various ways, such as disinfection or filtration.

Treating drinking water through disinfection

The goal of disinfection is to kill germs and bacteria. In smaller water treatment plants, our drinking water is usually disinfected using UV radiation. Larger water treatment plants, on the other hand, tend to use ozone and chlorine. Since this treatment method is the simplest, it is also the most commonly used in Switzerland.

In Switzerland, we have around 30 lake water treatment plants that purify surface water into drinking water. They pump lake water from a depth of 30 meters into the treatment plants. There, the lake water flows through various filters, such as rapid filters and activated carbon filters. This filtration process kills germs and algae in the water and disinfects it with ozone. Finally, the water is deacidified and chlorine is added. Once the lake water has passed through the treatment plant, it is fed into our drinking water network.

Treating drinking water through filtration

During filtration, our drinking water flows step by step through various filtration methods. A distinction is made between three filtration options: rapid filtration, slow filtration, and membrane filtration.

Rapid filtration

In rapid filtration, water flows through a layer of quartz sand. This process is intended to separate various particles from the water. It is similar to the natural filtration of spring water, which flows through different layers of soil and is thus purified.

Slow filtration

In slow filtration, the sand grains are finer, which is why the water flows through more slowly. This is where the name comes from. This treatment method already results in perfectly clean water.

Membrane filtration

Membrane filtration requires almost no chemicals and is the most environmentally friendly of these treatment methods. The water is forced through various ultrafiltration membranes. While germs and bacteria are not killed, they are completely separated from the water.

Of course, there are other treatment options. One is groundwater recharge, where the water seeps into the ground, flows through various soil layers, and is filtered naturally. Another option is to deacidify the water by adding hydroxides and soda, thus restoring a balanced pH value.

How does the water supply work in Switzerland?

In Switzerland, almost all households and industrial plants have access to safe drinking water at all times. This is ensured by approximately 2,500 water supply companies. Their goal is to provide safe drinking water even in emergencies and to ensure that the fire department has sufficient water available for firefighting at all times.

Drinking water quality Switzerland

Swiss drinking water is of very high quality. It is the product of years of investment and conflicts over its use. Various measures are in place to maintain this quality in the future.

Water quality control

On the one hand, water suppliers must regularly monitor water quality. On the other hand, they also have a duty to provide information. This means that they must publish their data at any time if required.

Water sampling and research

In addition, cantonal laboratories conduct ongoing random sampling. Furthermore, continuous research ensures the sustainable development of our water quality. Today, our analytical instruments are so advanced that even a single sugar cube dissolved in Lake Constance can be detected. These detailed analyses allow us to initiate necessary measures at an early stage.

Pesticides in Swiss drinking water

Switzerland is among the countries with the highest pesticide consumption. Due to high rainfall, pesticides can pose a significant threat to our waterways. To counteract this, pesticides are banned in protected zones around drinking water sources. Instead, alternative plant protection methods are to be promoted in the future.