Steady-State Water-Table Depressions Caused by Evaporation in Lands Overlying a Water-Bearing Substratum

Abstract

An explicit closed-form analytical solution giving the water-table depression is obtained for the steady-state problem of seepage to a water-bearing substratum from two reservoirs separated by a strip of land over which water loss by evaporation occurs at a constant rate. Two hydrodynamic situations can occur. In the first, there is only drainage into the substratum and all evaporating water originates from the reservoirs. In the second, the substratum, while accepting water draining from the reservoirs, also supplies some water to the evaporating surface. The method of boundary-value problems is used through the conformal mapping of a strip in the Zhukovskii plane to an auxiliary half-plane and reconstruction of the complex physical coordinate by the Signorini formula. The two hydrodynamic regimes are demarcated in the solution with the shape of the water table obtained in a closed form. The results of calculations show the effect of the evaporation rate, the hydraulic conductivity of the soil, the pressure in the water-bearing substratum, the distance between reservoirs, and the depth to the substratum. The method of boundary-value problems is also used to obtain an analytical solution for the water-table depression caused by evaporation from a strip in an infinite extent of land above a water-bearing substratum under pressure.