Dear Dnyaneshwar

of course barring natural river flow provokes major dysfunctioning of the river regime.

At least 7 major impacts, which importance depends on the goals of the dam:

- the seasonnal regime is modified, as the flows are being stored in the dam when they should run dowstream, and then during the dry season water is released when naturally there is poor flow

- the peak flood is lowered, to reduce the vulnerability to floods downstream

- the total volume flowed is reduced, both by evaporation from the dam's lake and by infiltration under the lake

- the ecology of the river is modified as the dam constitutes a discontinuity in the water course, with none or very limited connexion between upper and lower parts of the dam's lake

- the sediment transport regime is much modified, as most of the sediments are trapped into the dam's lake, with huge consequences dowstream up to the river mouth and the coastal area

- the geochemistry of the river is modified, mostly dowstream, because of the modification of river regime and a different partition of the origin of the flowing water downstream, and also because of possible unpredictable reactions in the sediments of the dam's lake

- the geomorphology of the river bed and floodplains is modified in the downstream part of the river up to the estuaries and river mouth, and coastal areas are also impacted.