Answer:
0.1365 m^3
Explanation:
thickness of upper aquifer = 500 ft
lower aquifer head drop = 150 ft
area of ground water basin = 12 m^2
specific yield of upper unit = 0.12
Storativity of lower unit = 4 * 10^-4
determine the amount of recoverable ground water
first step : calculate volume of unconfined aquifer Â
        = 12 * 500/5280  = 1.1364 miles^3
The recoverable volume of water from unconfined aquifer
= 1.1364 * 0.12 Â = 0.1364 miles^3
next : calculate volume of confined aquifer
    = 12 * 150/5250 = 0.341 miles^3
The recoverable volume of water from confined aquifer
   = 0.341 * ( 4 * 10^-4 )  = 1.364 * 10^-4 miles^3
Hence the amount of recoverable ground water in the basin
= ∑ recoverable ground water from both aquifer
 = 0.1365 m^3