Minimum Flow Requirement For Fish Population Affected By Dam Construction In Temperate Areas

Dam construction on rivers and streams provide desired benefi ts such as freshwater, hydroelectric power, and fi sh. Dam-related operation includes fl ow augmentation procedures such as fl regulation, fl ood releases or flfl ow releases, all of which have a detrimental impact on the downstream aquatic habitat like benthic macroinvertebrate zooplankton, phytoplankton and fi sh. In order to avoid negative impacts, a minimum fl ow release downstream of the dam is recommended. Minimum fl ow is the planned release of small amounts of water for ecological sustenance. During summer, the river to the downstream of the dam becomes dry which is detrimental from the fi shery point of view, as the migration of the fi shes is disrupted. Fishes are accustomed to live in flriver conditions, with their life cycle stages requiring the following factors: low silt content, well-oxygenated intra-gravel fl ows and minimum current, depth, velocity of water, dissolved oxygen. These factors are altered due to dam construction and restricted release of downstream fl ow. Fishes that feed on the invertebrate organisms like benthos and zooplankton are also affected by dammanipulated fl ow. In order to maintain the aquatic habitat downstream of the dam, authorities recommend minimum fl ow according to the habitat. The signifi cance of minimum fl ow is that it is needed to keep the streambed wet to an acceptable depth to support fi sh populations. This paper describes how minimum fl ow in the river, downstream of a dam, is the main requirement in the life cycle of fiwith respect to feeding habit and reproduction. The paper also gives examples of various dam-related recommended fl ows with respect to the life cycle of the fi sh.