Latitudinal analysis of rainfall intensity and mean annual precipitation in Chile

Roberto Pizarro1, Rodrigo Valdés1*, Pablo García-Chevesich2, Carlos Vallejos1, Claudia Sangüesa1, Carolina Morales1, Francisco Balocchi1, Alejandro Abarza1, and Roberto Fuentes1

The study and analysis of precipitation has become a crucial tool in understanding the temporal and spatial behavior of water resources, in terms of availability and impact on extreme events. The objective of this study was to evaluate different rainfall parameters (intensities for 1-h duration D = 1 h and return periods of T = 5 and 100 yr, and mean annual precipitation) for different latitudinal and climatic zones in Chile. We analyzed the information recorded on thousands of pluvial bands and rain gauges for 49 stations; this because it is unclear how rainfall intensities change along the country (though total amounts do), in addition to a lack of literature focused on ranges and amounts on the behavior of rainfall variables. The Gumbel probability distribution function (PDF) and mathematical rainfall intensity formulas were used to develop intensity-duration-frequency (IDF) curves for each station. Maximum and minimum rainfall intensity values for T = 100 yr ranged from 8.79 (hyperarid zone) to 40.17 mm h-1 (subhumid-humid zone). Total annual rainfall values ranged between 43.9 (hyperarid zone) and 3891.0 mm yr-1 (humid zone). Additionally, the real maximum intensity registered on each station was analyzed, determining its exceedance probability. Likewise, multiple comparisons were made to detect significant differences between the gauge stations and different climatic zones using the Kruskal Wallis test (alpha = 0.05). Differences between maximum and minimum values registered for all stations were as much as 80 times for total rainfall amounts and 4.5 times for rainfall intensities (T = 100 yr). However, maximum rainfall intensities values were similar at different latitudes, suggesting the absence of correlation between maximum rainfall intensity and annual rainfall amount, as the latter variable increased gradually with latitude.

Keywords: Precipitation, frequency-duration-intensity curves, IDF curves, rainfall intensity.
1University of Talca, Facultad de Ciencias Forestales, Casilla 747, Talca, Chile. *Corresponding author (rodrigovaldes@utalca.cl).
2University of Arizona, Department of Agricultural and Biosystems Engineering, Shantz Bldg #38, Room 403, PO Box 210038, Tucson, Arizona, USA.