Question

The ratio of the quantity of water stored in the root zone of the crops to the quantity of water actually delivered in the field is known as:

• A. Water use efficiency.
• B. Water conveyance efficiency.
• C. Water application efficiency.
• D. Water storage efficiency.

Answer 1

The correct option is C Water application efficiency.

(i) Water conveyance efficiency: It is defined as the ratio of the quantity of water delivered to the field or the irrigation land to the quantity of water diverted into canal system from the river or reservoir.

${\eta }_c=\frac{W_f}{W_r}\times 100$
$W_f=\text{Quantity of water delivered to field.}$
$W_r=\text{Quantity of water delivered into canal system.}$
It accounts for the water losses which occur in conveyance from the point of diversion into the canal system to the field.
(ii) Water application efficiency: It is defined as the ratio of the quantity of water stored in the root zone of the plants to the quantity of water delivered to the field.
$W_f=W_s+R_f+D_f$
${\eta }_a=\frac{W_s}{W_f}\times 100$
${\eta }_a=\frac{(W_f+D_f)}{W_F}\times 100$
$W_s=\text{Quantity of water stored in root zone}$
$W_f=\text{Quantity of water delivered to field.}$
$\text{It accounts for the water losses which occurs during the application of irrigation water to the field such as surface runoff}\left(R_f\right)\text{and deep percolation}\left(D_f\right)$

(iii) Water use efficiency: It is defined as the ratio of the quantity of water used beneficially including the water required for leaching to the quantity of water delivered.
${\eta }_u=\frac{W_u}{W_F}\times 100$
$W_u=\text{Quantity of water used beneficially.}$
$W_f=\text{Quantity of water delivered to the field.}$

(iv) Water storage efficiency: It is defined as the ratio of the quantity of water stored in the root zone during irrigation to the quantity of water needed to bring the moisture content of the soil to the field capacity.
${\eta }_s=\frac{W_s}{W_n}\times 100$
$W_u=\text{Quantity of water stored in root zone irrigation.}$
$W_n=\text{Field capacity - Available moisture in the soil prior to irrigation.}$
$\text{Water distribution efficiency}\left(n_d\right)\text{Water distribution efficiency evaluates the degree to which water is uniformly distributed throughout the root zone during irrigation and it is also known as uniformity coefficient.}$
${\eta }_d=[1-\frac{y}{d}]\times 100$
$d=\text{Average depth of water}$
$d=\frac{d_1+d_2+d_3+d_4....d_n}{n}$
y = Average numerical deviation in depth of water.
$y=\frac{|d_1-d|+|d_2--d|+|d_3-d|+...}{n}$