Question

The hourly observations at the mouth of a watershed due to 3 cm excess rainfall are given below. The area of watershed is ____ ha.

$\begin{array}{ccccccc}\text{Time (h)}& 0& 1& 2& 3& 4& 5\\ \text{Discharge}\left(m^2/s\right)& 0& 7& 24& 35& 26& 13\end{array}$

• A. 1260

Answer 1

The correct option is A 1260
$h=3cm$
$A=\frac{0.36\times \sum Ordinates\times \Delta t}{h}$
$=\frac{0.36\times 105\times 1}{3}=12.60k{m}^2$
$=1260ha$

Alternate solution,
$V=Qt$
$\Rightarrow Ah=Qt$
$\Rightarrow A=\frac{(0+7+24+35+26+13)\times 3600}{0.03}$
$=12.6\times {10}^6{m}^2=1260ha$