Question

If the irrigation efficiency is 80%, conveyance losses are 20% and the actual depth of watering is 16 cm, the depth of water required at the canal outlet is

• A. 10 cm
• B. 15 cm
• C. 20 cm
• D. 25 cm

Answer 1

The correct option is C 20 cm

Given: Irrigation efficiency/water application efficiency
${\eta }_a=80\%$

${\eta }_L=\text{Conveyance losses}=20\%$

$W_s=\text{Actual depth of watering}=16\text{cm}$

$W_f=\text{Quantity of water delivered to field.}$

${\eta }_a=\frac{W_s}{W_f}$

$W_f=\frac{16}{0.8}=20\text{cm}$

$\text{Water conveyance efficiency}={\eta }_c$

$=100-{\eta }_L=80\%$

${\eta }_c=\frac{W_f}{W_r}$

$0.8=\frac{20}{W_r}$

$W_r=\frac{20}{0.8}=25\text{cm}$