Towards more efficient soil-water modelling: moisture profiles with constant surface water content

Extract

There exists a large body of soil-water theory for ‘modelling’ soil-water movement and distribution. Yet simpler and sometimes cruder methods are often preferred. In part this preference is due to the fact that theory is not yet able to solve completely the more complicated situations that occur naturally, such as the intermittent application or removal of water in the presence of very hysteric soil-water properties. But in many instances it is due to the apparent difficulty of the analysis for the non-mathematically minded. For example, descriptions have been given of soil-water models, based on direct physical arguments, that are in fact finite difference analyses of the governing partial differential equations, but which make no reference to such equations or their existence. Indeed, the impression is sometimes given that soil-water physicists produce unnecessary, irrelevant and complicated analyses for something that is really quite simple. Unfortunately, the simpler approaches bypass possible complications that are revealed by the mathematically based analyses. It is therefore the purpose of this paper to take advantage of the close relation between the two approaches, and to draw attention to the steps that may be taken to avoid or reduce possible difficulties when following the simpler methods. In particular, it is hoped that the paper will lead to a more efficient use of computing facilities.