Laboratory studies on soil moisture flow and runoff generation in laterite soil

A study was conducted to analyse the saturated and unsaturated flow of water in laterite soil under selected precipitation intensities with a view to establishing a relation between hydraulic conductivity, moisture content and hydraulic head. Runoff generation and relation between runoff and soil moisture status were also considered. A rainfall simulator and soil trough were fabricated. The simulated raindrops resembled natural raindrops of size 5.4mm having terminal velocity of 9.29m/s. Instantaneous profile method was used to calculate the hydraulic conductivity. Experiments were carried out at rainfall intensities of 20, 40, 90 and 285mm/h at no slope condition and also at 10% and 20% slopes. The relation between hydraulic conductivity and volumetric moisture content was found to be exponential. The volumetric moisture content – hydraulic head relation was of the form H = a θ^β. Bedrock inclination was found a major factor governing subsurface drainage.