Spatiotemporal variability of precipitations and relationship with large-scale atmospheric indices in the Urubupungá Hydroelectric Cascade catchment area, Brazil.

The proper isolation of climate effects over the water resources needs accurate knowledge of the precipitation regime. The Urubupungá Hydroelectric Cascade catchment area (UHC) overlaps more than half Itaipu Hydroelectric Plant catchment area in the Paraná River, in Brazil, which recently faced its first ever predicted water emergency. This study determines the spatiotemporal patterns of both droughts and excessive precipitations in the UHC catchment area with the principal component analysis (PCA) and constant wavelet analysis (CWT) and their global teleconnections with composite analysis and cross-wavelet analysis (XWT). The precipitation data used include 166 rain gauges with 42 years length (1976–2017) and were indexed by the Standardized Precipitation Index (SPI) during the dry season, the wet season and the water year. The rotation of Empirical Orthogonal Functions (EOF) with the varimax method revealed five sub-regions of temporal patterns in the study area. The dry season was the only that showed consistent EOF in all sub-regions, whose temporal pattern showed gradual and instant changes both concentrated northern and instant changes mostly in the 1990 decade. The composite analysis presented both positive and negative anomalies directly related with precipitations over two atmospheric indices, which are the Pacific Decadal Ocean and the Atlantic Multidecadal Ocean. The teleconnections of UHC with atmospheric indices of the Antarctic continent oscillations should be deeply investigated, since it had strong influence in XWT analysis but a slightly behavior in the composite analysis. • The dry season over the upper Parana River basin has five distinct sub-regions of patterns and teleconnections. • The Northern sub-region concentrates the significant precipitation losses. • The Atlantic Ocean teleconnections strongly dictates the intensity of the convergence zone system over the study area. • The Atlantic Ocean teleconnections most pairedly dictates precipitations all over the study area. [ABSTRACT FROM AUTHOR]