The valley could be a U-shaped glacial valley, or V-shaped river valley or a broad synclinal valley. Flatlands and plains cannot make convenient places for reservoirs.

Reservoir yield is a measure for volume of water that can be drawn from a given reservoir in a certain interval of time and is also expressed in terms of safe or guarantee yield, secondary yield and design yield etc.

Generally small scale fault zones and shear zones can be treated by grouting. But in case of major shear zones, weak material would be excavated and space backfilled with hard material like concrete up to required depth.

A dam may be defined as a solid barrier constructed at a suitable location across a river valley with a view of impounding water flowing through that river.

Technically, site should be as sound as possible: strong, impermeable and stable strong rocks at site make job of designer much easy: he can evolve best designs.

An arch dam, as name implies, is an arch-shaped solid structure mostly of concrete, which is designed in such a way that a major part of thrust forces acting on dam are transmitted mainly by arc action, on to abutment rocks.

Distribution reservoirs are actually small storage reservoirs that hold water supplies in a water supply system for short spells of time.

A combination of series of arch dams called Multiple Arch Dams is sometimes applied with an advantage when valley is too wide for a single arch or gravity dam. Hence, arch dam can be constructed in a very wide valley too.

The greatest number of large dams are in Maharashtra (1508), followed by Madhya Pradesh (752); Gujarat (365), Karnataka (213), Orissa (149), Rajasthan (128) and Uttar Pradesh have a single large dam till twentieth century.

The geometry of joints, ir intensity, nature and continuity with depth, all must be thoroughly established and ir effects on site rocks evaluated and remedial measures taken in advance.