Delayed Drainage In A Stream-Aquifer System

Abstract

In a recent paper published in this journal, Higgins considered the problem of nonsteady flow from an unconfined aquifer into a fully penetrating stream in which the water level fluctuates in a prescribed fashion. To check the validity of his theoretical expressions, Higgins conducted a laboratory experiment with the aid of a sand box. The experimental results were in agreement with theory for the case where the water level in the stream declined linearly with time. However, when the water level in the stream was lowered instantaneously to its final position, the experimental drawdown of the water table at early time was higher than that predicted by theory; at large values of time, some of the experimental water table drawdowns were less than those predicted by theory. Higgins attributed this lack of correspondence between experiment and theory to a failure on the part of his theory to account for unsaturated flow above the water table. The purpose of this note is to develop an alternative theory which does not account for unsaturated flow and yet, is able to explain Higgins' experimental results.