When 3.5 million m3 of water was pumped out from an unconfined aquifer of 6.3 km2 areal extent, the water table was observed to go down by 2.5 m. The specific yield of the aquifer is best approximated as
When 3.5 million m3 of water was pumped out from an unconfined aquifer of 6.3 km2 areal extent, the water table was observed to go down by 2.5 m. The specific yield of the aquifer is best approximated as Correct Answer 22%
Concept:
Specific yield is defined as the volume of water released from storage by an unconfined aquifer per unit surface area of aquifer per unit decline of the water table.
Calculation:
Volume of water pumped out = 3.5 Mm3 = 3.5 × 106 m3
Area of aquifer = 6.3 km2 = 6.3 × 106 m2
The decrease in water table = 2.5 m
Specific yield = (3.5 × 106)/(6.3 × 106 × 2.5) = 0.22 = 22%
Other Important Points:
Specific Capacity is defined as the rate of flow through the well per unit drawdown that has determined for initial first meter fall of water in well.
Aquifer releases from storage, per unit mass or volume of aquifer, per unit change in hydraulic head, while remaining fully saturated.
The discharge corresponding to the critical head is called as critical or maximum yield. Allowing a factor of safety a working head is specified and the corresponding yield is from well is known as safe yield.
