barrage

n.
An artificial obstruction, such as a dam or irrigation channel, built in a watercourse to increase its depth or to divert its flow.

[French, from barrer, to bar, from barre, bar, from Old French. See bar¹.]

A structure built across a river or estuary in order to restrain or use water; for example, the barrage at La Rance, near St Malo, France. The Thames barrier was constructed for flood control, but other structures are built to store irrigation water. Some writers distinguish between barrages, built simply to restrain water, and dams, also used to generate hydroelectric power; others seem to distinguish between the two on the height of the structures (it is not unusual to read of dams and barrages on the Nile, for example) but these are not hard-and-fast distinctions.