The Necessity of Using Large-scale Field Rainfall Simulator to Investigate Soil Erosion and Interception

Due to the logistical challenges of large-scale rainfall simulator, most studies to date have used small scale rainfall simulator with a nozzle height of less than 3 m and a plot area of less than 5 m 2. Performing such small-scale studies is valuable for investigating the rate of soil erodibility, soil infiltration, the impact of herbaceous and shrub cover on water erosion and runoff. But there is a need for larger rainfall simulator to better understand and deepen the water cycle process and the interactions that occur on a larger scale. The rainfall simulator should be designed to simulate rain from top of canopy. In this case, raindrops can reach their final speed. For this purpose, a 15-meter anchored tower (controlling tower by several cable is called anchoring) with multiple nozzles is need. The most important component of any rainfall simulator is the type of nozzle used. The most common type of nozzle is a rotating plate nozzle with a 360 ° rotation angle in two linear mounting patterns and H mounted on top of the mast. The nozzles are connected vertically to a water tank and pump motor via a plastic pipe. After setting up the system and calibrating the rainwater, a windmill collector with a radius of 5 meters (about 80 m 2) of thick nylon, thin rods and zippers is used to collect throughfall, interception, and stemflow. In water erosion of soil, the most important stage that the soil is washed is rutting stage. In small-scale rainfall simulator, the low dimensions of plots causes runoff doesn’t have enough time to rut the soil, so in this condition true knowledge about soil erodibility cannot be achieved.