Question

A S-curve derived from a 6 hr unit hydrograph for a catchment having area 480 km${}^2$. The equilibrium discharge for this catchment will be

• A. $22.24m^3/s$
• B. $222.4m^3/s$
• C. $111.24m^3/s$
• D. $11.24m^3/s$

Answer 1

The correct option is B $222.4m^3/s$

$Q=2.78\times \frac{A}{T}$
$=2.78\times \frac{480}{6}=222.4m^3/s$

Alternatively,
At equilibrium , all rainfall converts into runoff.
$Q=(R.I.)\times A$
$=\left(\frac{1}{6}cm/hr\right)\times 480k{m}^2$
$=\frac{1}{6}\times \frac{{10}^{-2}}{3600}\times 480\times {10}^6$
$\simeq 222.4m^{3/}s$