Débit réservé et autres précautions piscicoles actuellement imposées lors de l'installation de microcentrales hydroélectriques en Auvergne-Limousin

Abstract

In France, authorization is required from the Prefect's office (department administration level) before a hydroelectric power station of less than 500 kW* gross power ("micro-power station") can be built. The legislation on this was made many years ago (Law of 1919) and is relatively literal. Since 1974, as a result of an increasing number of projects carried out in the seven departments of Auvergne and Limousin, and awareness of environmental protection problems, authorization have been generally accompanied by more stringent requirements to be complied with by the construction. Until more accurate technical and scientific data becomes available on the extent to which these dams affect fishbreeding, a "basic legal minimum flow" (BLMF) is prescribed which may range from 70 to 130 % of the characteristic rate of flow of the river. This coefficient is proposed by the regional board of the Firshery Office in accordance with quality of aquatic life, accessibility for angling and length of river diverted (generally several hundred metres for every 4 km). The basic minimum flow selected is regulated as follows : A lower value (minimum 0.7 BMLF) during the cold season. A higher value (maximum 1.3 BMLF) during the warm season (april to september), when invertebrate production and trout-growth are at a high level, and electricity requirements are usually lower. Construction of a fish-ladder and a simple flow control device is almost always required. The authorities usually seek advice from anglers' associations and the regional board of the Fishery Office (technical department). * Since july 1980, this limit is 4 500 kW.