Hydro graph Principles

Question 1

UUH Principles

Answer 1

Linearity
Principle of superposition

Time invariance
A system is said to be time invariant when its
parameters do not change with time.

Question 2

Hydrograph for rainfall

excess Δt from UH

Answer 2

Consider the UH u(t), for a given
catchment and rainfall duration Δt.
Assuming the catchment has a linear
response, the runoff hydrograph, Q(t), for
a rainfall excess P over a duration Δt is
given by:

Question 3

Use of UH for rainfall excess

being multiple of Δt

Answer 3

If the rainfall excess, P, occurs over a
duration equal to an integral multiple of Δt,
say nΔt then:

Question 4

UH for any duration

Answer 4

S-Hydrograph
For storms in which the duration of the
rainfall excess is not an integral multiple
of Δt, use is made of a S-hydrograph.
S-hydrograph is the response to a storm
of infinite duration.