Resumen
In this work, several results are presented on the variability of monthly water inflow volumes (MIV) for the dams located on the rivers of the Gulf of California continental watershed. Monthly series of the Pacific Decadal Oscillation index PDO (1900 to 1999), rainfall (1921 to 1999), and MIV (1939 to 1999) were used for the analyses. Applying the Varimax Rotated Empirical Orthogonal Function analysis to MIV series, "Northern" and "Southern" regions were separated, being this result in agreement with the climatic characteristics of the study area. The rainfall-PDO relationship was found to be in-phase in winter for both regions during the entire analyzed period (1921-1999). In summer, the relationship was out-of-phase during 1956-1974 and in-phase in 1987-1991 for both regions. The results show a stable relationship in winter between the rainfall and the oceanic conditions, which agrees with the arid character of the study zone. In summer, the results imply a more remarkable influence of other than local factors of climate variability, like the mesoscale convective systems, the Mexican Monsoon and the Pacific tropical storms, the main sources of humidity in summer. The relationship between rainfall and PDO-index in winter suggests that during the next decade, in which the PDO seems to change to its cool phase, winters could continue to be dry and the inflow volumes for the dams could continue to be below normal.