TR(BR)-142 : Evaporation from layered soils in the presence of a water table soil strata and ground water quality

Abstract

Evaporation of water from soil surface causes loss of water and is also responsible for salinizing the top layers of the soil. The danger of soil salinization becomes more acute in regions where a high ground water table exists. In order to minimize water losses as well as reduce the rate of soil salinization, one has to evaluate the effect of the depth of soil layers overlying the water table.

Evaporation from shallow water table through a homogeneous soil profile has been studied theoretically and experimentally by many workers. However, uniform soil profiles rarely occur in nature. It is more common to find the soils having well-defined layers differing from each other either in texture or in structure. Therefore, it becomes necessary to determine the effect of layered soils on evaporation from a shallow water table.

The purpose of this study is to estimate the steady state evaporation rates from layered soils in the presence of high water table under isothermal conditions. A finite difference numerical scheme based upon the one-dimensional Richards equation has been employed to estimate the evaporation rates from a two-layered soil profile overlying a shallow water table for appropriate initial and boundary conditions. The method takes into account the relevant atmospheric factors and soil moisture characteristics of the two layers. The effects of sequence and thickness of the soil layers and water table depth on the evaporation rates have been examined.