Analyzing the Influence of Spatial Variations on the Performance Metrics of a Rainfall Simulator

This study provides a comprehensive analysis of the significance of rainfall simulator (RS) in hydrological research and investigates the effects of spatial variations on rainfall parameters. Rainfall simulators enable detailed examination of environmental variables under controlled laboratory conditions without relying on natural rainfall. However, the assumption of homogeneity in parameters such as rainfall intensity, uniformity, and drop size can lead to the neglect of spatial variations within the study area, thereby limiting the accuracy of the results. This limitation is particularly critical in studies focused on erosion, drainage, and infiltration, where spatial variations play a key role and may lead to misleading conclusions. In this study, performance parameters were evaluated across nine sub-regions along the simulator channel under four different rainfall intensities (40, 70, 80, and 100 mmh⁻¹). The effects of rainfall intensity on spatial uniformity and drop size were thoroughly analyzed. The findings reveal significant spatial variations in rainfall distribution. Notably, higher rainfall intensities were recorded in the middle regions resulting in higher uniformity values in these areas. Although the evaluation of uniformity coefficients for the entire area under 40 mmh⁻¹ and 70 mmh⁻¹ rainfall intensities yielded debatable results, sub-area analyses indicated that this uniformity did not hold true for the majority of the channel. Overall, a predominantly uniform rainfall distribution (>80%) was observed. Regarding drop sizes, spatial differences were identified, with a slight increase in drop size as rainfall intensity increased. These findings emphasize that treating rainfall parameters as a single fixed value for the entire study area may fail to fully capture the dynamic nature of natural rainfall. Considering spatial variations is essential for achieving more reliable and accurate results