90% of all water withdrawn are environmentally significant because in doing so, more than half of the natural minimum river discharge is removed. The diagram below illustrates the number of water withdrawal sites dedicated to power generation in Switzerland licensed before or after the effective date of the new Water Protection Act (WPA).

In addition, the diagram indicates the number of water withdrawal sites that have an environmentally significant impact.

Interpretation example
Before the Water Protection Act entered into force in 1992, 1,253 water withdrawal sites for power generation were licensed, with 1,116 of them having a significant environmental impact.

Comments
• Data are based on the Map of Residual Flows in Switzerland (Kummer et al., 2007).
• Only water withdrawals for power generation are recorded. If more than half of the natural minimum river discharge is removed, withdrawals are considered to be environmentally significant.
• The E11 indicator does not cover withdrawals from watercourses that periodically run dry, withdrawals for military purposes, and withdrawal sites that, even though legally licensed, did not have operational withdrawal equipment in late 2004.
• The largest part of today’s water withdrawals had been granted before the new Water Protection Act entered into force in 1992. Most of these licenses will not expire until the period of 2030 to 2050. Withdrawal sites licensed after 1992 must guarantee residual flow volumes as stipulated by the Water Protection Act. Operators of withdrawal sites licensed before 1992 possibly observe the conditions of the Water Protection Act on a voluntary basis.

For details on water withdrawn at various altitudinal vegetation zones, please refer to the complete E11 datasheet.

Power generation requires large volumes of water to be withdrawn from brooks and rivers, frequently resulting in water in residual flow stretches below withdrawal sites to run very low. In combination with water pollution and river bank stabilization, this development has far-reaching consequences. Many native fish species, for example, have been redlisted. In order to survive, fish primarily need sufficient amounts of water. Low residual flows are often subject to wide temperature fluctuations, affecting the development of numerous water organisms. Species adapted to strong currents lose their preferred habitat due to lowered discharge rates. Moreover, when brook and river bottoms are being clogged with fine deposited material, suitable spawning sites are destroyed.
Residual water running too low can also cause the groundwater table to drop, since less water will seep into the subsoil. Wetlands such as reed meadows will eventually dry up due to lack of water-logging, which in turn deprives moisture-loving plants of their basis for survival, so they, too, will disappear.
Residual flow stretches that temporarily run dry have lost their value for water organisms. Such stretches are poor in species even if they run water most of the time.
It is not only significant water withdrawals that have an ecological impact on watercourses: very irregular discharges will upset the habitats of numerous water organisms as well. One third of Switzerland’s watercourses is affected by swell operation of hydroelectric power plants.
In addition to negative ecological effects, extremely low amounts of residual flow also reduce the attractiveness of brooks and rivers to humans.

Responsible for E11
Lukas Kohli, kohli@hintermannweber.ch, +41 (0)31 312 82 72
Expert FOEN contact: Manfred Kummer, manfred.kummer@bafu.admin.ch, +41 (0)31 322 93 93

Additional sources of information
> Federal Office for the Environment FOEN

> Complete E11 datasheet (512 KB)

This information is based on the document 800 326.10 Produkt E11 V1_en.doc dated July 12, 2009.
Data will be updated once the next update of the Map of Residual Flows has been finalized.