Depending on the function served and the range in reservoir head under which it is to operate, the discharge capacity and frequency of reservoir draw down, intakes for hydroelectric projects may be relatively simple submerged intakes or more elaborate structures raised as a tower above maximum reservoir level. Intakes may also be classified as low pressure and high pressure intakes though there is no clear line of division between the two classes of intakes; the essential requirements of the two types being the same, but may differ in details and type of equipment on account of the difference between the depths of water in which they are to be operated.

Broadly the intakes are classified as

(i) Run-of-the river type, and

(ii) Reservoir type.

1. Run-of-River Intake. In run-of-river powerplants, intake is appurtenant to power house and draws water from the river without any appreciable storage upstream of the diversion structure (Fig20.35). characteristics of river flows, the intake is designed to withstand high peaks and short duration flood flows and high sediment loads. The bell mouth entrance is essentially provided with trash-rack.

Canal intake. It is also a variant of the run-of-river intake, that is provided adjacent to the diversion weir/barrage to admit water int the canal (Fig.20.36). it is designed to function under low heads and the topography and geology permits straight for it.