MODIFICATION AND PERFORMANCE EVALUATION OF A SMALL-SCALE RAINFALL SIMULATOR

Rainfall simulator is an essential tool to simulate natural rainfall accurately and precisely. A reliable, accurate and portable small scale rainfall simulator is required for runoff, infiltration, sediment generation and erosion studies. And this has been used extensively to gather runoff, infiltration and erosion data in both laboratory and field experiments. This study was conducted to determine rainfall intensity, rainfall drop sizes and erosivity. An existing rainfall simulator was modified to be easily assembled, transported and maintained as well as to create a variety of rainfall regimes. Performance evaluation of the modified rainfall simulator was carried out with 10 trials to determine the intensity of rainfall, drop sizes and erosivity. Correlations were drawn out between the data of the simulated rainfall and that of the natural rainfall data. The results show that rainfall amount, intensity and kinetic energy are the main variables that influence rainfall erosivity index at 99% confidence level. The erosivity index of both simulated rainfall and natural rainfall are 36395.40JM-2mmhr-1 and 34792.51JM-2mmhr-1, respectively. The results of regression analysis of the simulated and natural rainfall show the influence of intensity and amount of rainfall on erosivity index. The linear regression models of simulated and natural rainfall show strong influence to varying degrees of (R2-values) which are 0.949, 0.190, 0.949 and 0.955, respectively. It was concluded that the modified rainfall simulator is suitable to simulate and reproduce natural rainfall characteristics such as rain drop size, intensity, kinetic energy and erosivity. The modified rainfall simulator is a portable type which can be easily assembled, maintained, transported and it can also be used in both laboratory and field experiments for irrigation, infiltration, runoff, sediment and erosion control studies. The estimated cost of modification was ₦44,520.00.