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Abstract
Land drainage is defined as, the removal of excess surface and subsurface water from the soil. Soil is considered a porous medium that is defined as continuous solid phase,
which has many void spaces, or pores. Land drainage achieves managing ground
water level and removing soluble salts from the soil to enhance soil workability, air water balance and crop growth and consequently increase crop production. Therefore,
when designing a system for an area, the designer engineer must use certain criteria to control the ground water table.
The drainage design criteria are classified into agricultural, technical, environmental,
and economical criteria. Agricultural design criteria are the criteria that specify the highest permissible levels of water table on or in the soil. The technical drainage criteria are related to the performance of the drainage systems, and are based on the
drain discharge, spacing, slope and diameter of the drains. The environmental design criteria are used to minimize ant expected environmental damage. Moreover, the economic design criteria are used to maximize the net benefits through optimizing the design of the drainage systems.
Unfortunately, up till now, traditional design formulae that suffer from many
shortcomings are in use. They though easy to implement, they do not take into
account the various soil properties, effect of water flow through porous media (soil) under thermal ffects .and to study evaporation and the effect of root water uptake on the design process. Thus, the objecti ves of the study were formulated to simulate the
unsteady two dimensional the effect of incorporating evaporation from the soil surface and root water uptake on the design criteria of the subsurface drainage systems.
To achieve the objectives of the study a coupled mathematical model was exploited to study the effects of the two dimensional heat transport through porous media on the water flow through porous media under unsteady state conditions. The coupled model
consists of two sub-models of water and heat transport through porous media that are coupled with coupling terms. The mathematical formulation of the water and heat transport sub-models was developed. In addition, the numerical solution of the mathematical formulations was developed by Galerkin finite element method (FEM).