Executive Summary

This document describes the computer model SoilCover which can be used for the analysis of flow of water between the soil surface and the atmosphere. Predicting the flow of water between the soil surface and the atmosphere is a critical issue in the design of soil covers for mine tailings, acid generating waste rock, and other land based disposal systems. Water movement through soils can be thought of as a three component system consisting of the soil-atmosphere interface, the near surface unsaturated zone, and the deeper saturated zone. SoilCover is a soil-atmospheric flux model that links the subsurface saturated / unsaturated groundwater system and the atmospheric systems above the soil in an attempt to represent the soil-atmosphere continuum.

The current version of SoilCover is being released for use as a research and design tool for modelling cover performance. Therefore the program is to be used solely at the discretion of the user with due diligence. The main objective in applying SoilCover is to evaluate alternative cover designs with respect to drying and desaturation under atmospheric conditions. The flow of moisture between the soil and the atmosphere is a complex process in which three factors dominate. The first factor is the supply of and demand for water imposed at the soil surface by atmospheric conditions such as total precipitation, net radiation, wind speed, and air temperature. The second factor is the ability of the soil to transmit water and the associated water regime, controlled by hydraulic conductivity and storage characteristics. The final factor involves the influence of vegetation. The type and density of vegetation affects evaporation through the consumption of water through root uptake, and also runoff rates and surface retention.

SoilCover is a one dimensional finite element package which models transient water and heat transport in a soil profile, and can be used in conjunction with other commercially available flow modelling packages such as the HELP model. It uses a physically based method for predicting the exchange of water and energy between the atmosphere and a soil surface. The theory is based on the well known principles of Darcy's and Fick's Laws which describe the flow of liquid water and water vapour, and Fourier's Law to describe conductive heat flow in the soil profile below the soil/atmosphere boundary. SoilCover predicts the evaporative flux from a saturated or an unsaturated soil surface on the basis of atmospheric conditions, soil properties and conditions, and vegetative cover.

SoilCover requires an IBM compatible 386DX or higher with a math coprocessor. The program user will require a background in moisture flow in soils, climatology, finite element and numerical modelling.

Last Modified: 2003-11-26		Important Notices

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