This note describes the technical characteristics and the preliminary setup and calibration of a nozzle-type rainfall simulator installed at the University of Perugia's Masse experimental station. This simulator includes some innovative features, usually not present in similar low-cost instruments employed in field experiments: 1) both single and multi-nozzle operation are feasible, thus enabling the possibility to simulate variable-intensity rainfall events; 2) events are simultaneously reproduced in two identical plots (width 1 m, length 0.92 m, and slope 16%), thus obtaining two replications for each experiment; 3) the runoff volume coming from the micro-plots and the water volume falling outside the plots are both collected and conveyed to separate outlets, thus allowing an easy calculation of the infiltrated volumes and of the system efficiency. The first step of the calibration regarded the spatial distribution of rainfall, the stability of the rainfall intensity over time (within the experiment), and the reproducibility of the rainfall intensities both in space (between the two plots) and over time (among successive experiments). Next, the drop size distribution (DSD) and the related rainfall characteristics (median volumetric drop diameter D50 and mean kinetic energy per unit area and unit depth) were evaluated by the oil method for the single and some multi-nozzle applications. An effective automatic drop recognition procedure by the Fiji open-source software is proposed and illustrated. Results indicate a high uniformity of rainfall (Christiansen uniformity coefficient > 92%) in both single and multi-nozzle operation for both plots. The reproducibility of experiments over short time intervals and under similar environmental conditions is satisfactory (coefficient of variation of mean intensity < 3%). Comparing initial and final rainfall intensity values, a slight decrease was observed within each experiment (about 2% on average). Some systematic differences in rainfall intensity were also detected between the plots. The analysis of both the intensity and the DSD in the multi-nozzle operation indicated the presence of some interference among the individual sprays when larger nozzles are simultaneously activated. Moreover, in agreement with the literature, it was confirmed that this type of rainfall simulator always produces kinetic energy values lower than those associated with natural rainfall of similar intensity
Setup and calibration of the rainfall simulator of the Masse experimental station for soil erosion studies
Vergni, L.
;Todisco, F.;Vinci, A.
2018
Abstract
This note describes the technical characteristics and the preliminary setup and calibration of a nozzle-type rainfall simulator installed at the University of Perugia's Masse experimental station. This simulator includes some innovative features, usually not present in similar low-cost instruments employed in field experiments: 1) both single and multi-nozzle operation are feasible, thus enabling the possibility to simulate variable-intensity rainfall events; 2) events are simultaneously reproduced in two identical plots (width 1 m, length 0.92 m, and slope 16%), thus obtaining two replications for each experiment; 3) the runoff volume coming from the micro-plots and the water volume falling outside the plots are both collected and conveyed to separate outlets, thus allowing an easy calculation of the infiltrated volumes and of the system efficiency. The first step of the calibration regarded the spatial distribution of rainfall, the stability of the rainfall intensity over time (within the experiment), and the reproducibility of the rainfall intensities both in space (between the two plots) and over time (among successive experiments). Next, the drop size distribution (DSD) and the related rainfall characteristics (median volumetric drop diameter D50 and mean kinetic energy per unit area and unit depth) were evaluated by the oil method for the single and some multi-nozzle applications. An effective automatic drop recognition procedure by the Fiji open-source software is proposed and illustrated. Results indicate a high uniformity of rainfall (Christiansen uniformity coefficient > 92%) in both single and multi-nozzle operation for both plots. The reproducibility of experiments over short time intervals and under similar environmental conditions is satisfactory (coefficient of variation of mean intensity < 3%). Comparing initial and final rainfall intensity values, a slight decrease was observed within each experiment (about 2% on average). Some systematic differences in rainfall intensity were also detected between the plots. The analysis of both the intensity and the DSD in the multi-nozzle operation indicated the presence of some interference among the individual sprays when larger nozzles are simultaneously activated. Moreover, in agreement with the literature, it was confirmed that this type of rainfall simulator always produces kinetic energy values lower than those associated with natural rainfall of similar intensityI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
