Question

Calculate the water distribution efficiency if the depths of penetration along the length of a border strip at an interval of 20 m are 1.5 m, 1.8 m and 2.1 m respectively.

• A. 0.6667
• B. 0.8333
• C. 0.8889
• D. 0.9767

Answer 1

The correct option is C 0.8889

Given that: The observed depths at three stations are:

$y_1=1.5\text{m},y_2=1.8\text{m and}{y}_3=2.1\text{m respectively}$

Water distribution efficiency
$\left(n_d\right)=[1-\frac{y}{d}]\times 100$

where y = Average numerical deviation is depth of water stored from the average depth of water 'd' stored in the root zone during irrigation.

$\text{Mean depth}\left(d\right)=\frac{(1.5+1.8+2.1)}{3}=1.8\text{m}$

and the average of absolute values of deviation from the mean :
$y=\frac{(|1.5-1.8|+|1.8-1.8|+|2.1-1.8|)}{3}=0.2\text{m}$

$\text{Then, water distribution efficiency}\left(n_d\right)=[1-\frac{y}{d}]\times 100$

$\therefore n_d=(1-\frac{0.2}{1.8})\times 100$

$n_d=88.89\%$