Mumbai University > Civil Engineering > Sem 7 > Irrigation Engineering

Marks: 6M

Year: Dec 2015, May 2016

A unit hydrograph is a hydrograph representing 1 cm of runoff from a rainfall of some unit direction and specific areal distribution. Unit duration refers to the duration of a run off producing rainfall-excess that result in a unit hydrograph.

Significance of Unit hydrograph:-

1. The effective rainfall is uniformly distributed within its duration of specified period of time.
2. The effective rainfall is uniformly distributed throughout the whole area of drainage basin.
3. The base or time duration of the hydrograph of direct run-off due to an effective rainfall of unit duration is constant.
4. The ordinates of direct run-off of common base-time are directly proportional to the amount of direct run-off represented by each hydrograph.

S-hydrograph or S-curve is a hydrograph that is produced by a continuous effective rainfall at a constant rate for indefinite period. It is a continuous rising curve, in the form of letter S, till equilibrium is reached.