UNSTEADY DRAWDOWN OF WATER-TABLE

This paper deals with the development of equations to predict watertable geometry for flow toward a drain ditch or reservoir whose water surface level is subject to a sudden specified drop. A closed function representing the watertable geometry is obtained for the classical potential formulation of the problem under initial and boundary conditions related by means of perturbation method. The first-order term of this closed function is identical to the solutions published by Higgins (1980), for large values of time, by Stallman (1962), and by Bear (1974). The inclusion of the second and third order terms improved the accuracy considerably. The water table profile found as a function of only one variable is predicted for various u, = -d0/h0 values, ranging between - 1 and 0. Temporal and spatial variations of the water table are obtained for various u. values. The comparison of the present results with those of previous works is also presented. © ASCE.