Evaluación y análisis de la intensidad de lluvia de diseño influenciada por oscilaciones decadales de precipitación mediante la determinación de una metodología de cálculo para la cuenca del río Paute

Abstract

In the Paute river basin, spatial and temporal variabiliy in precipitation levels has been recorded. As a resultof this temporal variability, positive and negative perturbations were determined, causing decadal oscillations of precipitation. These oscillations contain periods with high average rainfall (wet) and others with lower averages (dry). These periods are within a growing or decreasing trend depending on the season analyzed. The existence of wet and dry periods represent a marked difference in the annual averages, considering this as climate variability. On the other hand, the increasing or decreasing tendency in the averages has been established as climate change. In other basins, mainly European, significant differences have been found in the results of analysis of extreme events when different recording periods are used. Likewise, the updating of intensity-duration-frequency curves (IDF) has shown that the magnitudes differ for analyzes performed with different periods of rainfall information. This study focused on determining the differences in extreme rainfall by analyzing different periods of records in 8 stations in the basin. The time interval in which these records are analyzed is determined by the wet, dry periods and their transitions (increasing and decreasing), within the decadal oscillations of precipitation. Due to the spatial variability in the precipitation distribution in the basin (unimodal and bimodal regimes), the Gumbel, Gamma and Log-Pearson type III distributions (three-parameter gamma) were used. The best fit choice was made by the Kolmogorov-Smirnov test. To reflect differences between extreme events by their intensities, the equation for IDF curves best adjusted to each station was chosen. It was observed that the events for wet periods were equivalent to events of greater return period when the complete series of records was analized. Likewise, the extreme rains of dry periods were equivalent to a shorter return period. Finally, the existence of hysteresis was evidenced in two of the four stations located at the center of the basin and belonging to the bimodal regime