When it comes to drinking water, Berlin is self-sufficient. The local groundwater covers the needs of the city. In 2008, nine waterworks processed around 205 million cubic metres of groundwater to provide drinking water. Twenty years earlier, the demand was still almost twice as high.
Waterworks pump groundwater through wells directly into their treatment plants. Therefore, waterworks can be found in areas with lots of water: this includes Spandau and Tegel in the northwest, Kladow in the southwest and Kaulsdorf or Johannisthal in the southeast. The Stolpe waterworks also supply Berlin with water from Brandenburg.
To protect the groundwater from contamination, the pumping wells are embedded in water conservation districts. These are divided into different conservation zones. The closer to the well, the stricter the regulations.
Conservation Zone I is defined as the area in the immediate vicinity. Only measures required for water supply purposes are permitted here. In Zone II, neither houses nor roads may be built. In Zone III, waste water may not be discharged into the ground. Oil changes are prohibited here, for example.
The zones are defined based on the time it takes for the groundwater to reach the well. In the innermost conservation zone, it takes about 50 days. In the outermost zone, it can take up to 12 years in urban catchment areas; and up to 30 years in areas that are in danger of contamination due to agriculture and forestry.
East Berlin was subject to other regulations with larger conservation zones. After German reunification, the zones were adjusted to match the regulations above. Today, almost 24 percent of the city are part of a water conservation district.