Downstream fish passage technology is much less advanced than it is for upstream fish passage facilities. This is simply due to the fact that efforts to re-establish free movement for migrating fish began with the construction of upstream fish passage facilities, and that downstream migration problems have only been recognised and addressed more recently. It is also because it is much more difficult and complex to develop effective facilities for downstream migration. This situation is not restricted to France, since as yet, no country has found satisfactory solutions for downstream migration problems, especially where large installations are involved (EPRI, 1994).