Construction and calibration of a portable rain simulator designed for in situ researches of soil resistance to erosion

Abstract

Land degradation caused by erosion processes is a widespread global problem. A rain simulator is one of the tools often used to determine the resistance of soils to erosion processes. The aim of this publication is to present the process of construction and calibration of a small, portable field simulator which would be implemented in researches designed to determine the changes of soils’ shear strength parameters in forested areas (in situ) caused by the change of soil moisture content achieved by rain simulation. The constructed simulator consists of a metal frame, sprayers (with specific nozzles), a sediment funnel/tray made of metal, water and sediment collector unit, a water tank and pump, and a set of rubber hoses, manometer, valves, reducers, adapters and other supplementary equipment. The calibration was carried out by using the pluviometer method. The choice of nozzles was based on the criteria of low water consumption (losses), high uniformity coefficient (CU) and the possibility of achieving the intensity of downpour rains specific for the investigated area. Further calibration of the device consisted of determining the raindrop diameter and the distribution of rainfall when the simulator is positioned on slopes (7° and 15°). The achieved rain intensity was 1.7-1.9 mm.min-1 , with a uniformity coefficient (CU) of 92.23-93.70% for raindrop diameters (D50) equal to 1.2 mm. The kinetic energy of simulated rain (Ke) was 2.82∙10-6 J. The constructed simulator proved itself to be in accordance with all of the criteria given, and it can successfully be implemented in researches aimed to determine the resistance of forest soils to erosion processes, infiltration, and sediment yield.