Water Storage Efficiency ($\eta_s$) is defined as the ratio of:
Options:
(A) Water stored in the root zone during irrigation to the water needed in the root zone prior to irrigation
(B) Water delivered to the field to the water diverted from the source
(C) Water beneficially consumed by crops to the total water applied
(D) Water stored in a surface reservoir to total annual runoff
Answer Key:
A
Step-by-Step Solution & Explanation
Water storage efficiency evaluates whether the irrigation adequately replenished the root zone moisture deficiency:
$\eta_s = \frac{W_s}{W_n} \times 100$
where $W_s$ is water stored in root zone, and $W_n$ is water needed to bring moisture up to field capacity.