Question

Rainfall depth over a watershed is monitored through six numbers of well distributed rain gauges. Gauged data are given below
$\begin{array}{ccccccc}\text{RAIN GAUGE NUMBER}& 1& 2& 3& 4& 5& 6\\ \text{RAINFALL DEPTH (mm)}& 470& 465& 435& 525& 480& 510\\ \text{AREA OF THIESSEN POLYGON}& 95& 100& 98& 80& 85& 92\\ (\times {10}^4{m}^2)& & & & & & \end{array}$


The Thiessen mean value (in mm, up to one decimal place) of the rainfall is_____

• A. 479.1

Answer 1

The correct option is A 479.1
$\text{Mean value of rainfall =}\frac{\sum A_i{P}_i}{\sum A_i}$
$=\frac{(470\times 95)+(465\times 100)+(435\times 98)+(525\times 80)+(480\times 85)+(510\times 92)}{95+100+98+80+85+92}$
$=\frac{263500}{550}=479.09mm$
$\simeq 479.1mm$