Aging Dams : Removal or not ?
An increasing number of these structures are approaching the end of their economic and technical life span.
As a rule this is the case after 70-100 years. In many states the duration of operation is regulated to be within the framework of the concession, so a life span of 50-80 years.
In most European countries (with the exception of some Eastern countries, and the ex-Soviet Union) almost every dam is under a concession which lasts from 40 to 60 years. This period is usually smaller than the physical lifetime of the building.
These concession, granted by the state, are defining, depending on the state :
- the aim of the structure (type of production),
- the methods of exploitation,
- minimum flow release
- ownership of the equipment, powerhouse and dam during and after the end of the concession
- what has to be done if the concession stops (renaturalisation, renewal of the concession etc.)
- from time to time, who has to pay the renaturalisation
- the taxes
Some countries have other types of concessions: Criteria can be: size, power capacity, height or length of the dam, reservoir volume , private or public ownership. For little dams smaller than approx. 5 m and especially in the case of very old dams, concessions are often incomplete or inexistant
As a consequence, it is anticipated that in the near future, there will be a veritable wave of medium-sized and large dams that become obsolete. In every single case questions can be raised; should the operation be discontinued? can the construction be modernised or dismantled?
The same questions apply to small transverse structures, many of which are no longer functional.
The time for an evaluation has come, the removal or conversion creates an exceptional opportunity to the benefit of the clearly urgent rejuvenation of our rivers and the re-creation of the ecological free passage for migrating fish and debris.