Transient Radius of Influence Model

Abstract

In the traditional analysis, the radius is defined as a constant radial distance beyond which the aquifer is undisturbed by the pumping of water from a well. In the real world, the radius is a transient variable. Its value is zero when the pumping starts, and it expands radially in the aquifer as pumping proceeds. A transient radius of influence is a proper concept to describe well hydraulics. Traditional analyses in well hydraulics were focused on water table drawdown, and less attention was given to the cone of depression volume. From the conservation of mass principle, the cone of depression volume is related to the amount of water removed from the aquifer and is, therefore, related to the pumping time. Such an concept is employed to obtain transient solutions of well drawdown and radius of influence for a well in an unconfined aquifer under a constant recharge rate.