While porosity is a measure of the water-bearing capacity of the formation, all this water cannot be drained by gravity or by pumping from wells, as a portion of the water is held in the void spaces by molecular and surface tension forces. The volume of water, expressed as a percentage of the total volume of the saturated aquifer, that [...]
Ground water moves from levels of higher energy to levels of lower energy, its energy being essentially the result of elevation and pressure, the velocity heads being neglected since the flow is essentially laminar. The velocity is very small in the laminar range—of the order of 1 cm/sec—and the Reynolds number (Re) for ground water flow varies from 1 to [...]
The specific capacity (Q/sw) of a well is the discharge per unit drawdown in the well and is usually expressed in lpm/m. This is a measure of the effectiveness of a well. From Eqs. (4.78), (5.89) and (5.90). Which shows that the specific capacity of a well is not constant but decreases with the increase in pumping rate (Q) and [...]