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A few aspects of spatial variability, connected with climate variability, in the Rio de la Plata basin are analysed through changes in the basin runoff considered as indicative of the annual integrated precipitation. Those changes contain better information on climate variability than the sparse records of precipitation and temperature in view of the high spatial and temporal variability of those parameters. The precipitation data are applied in the most active zones of the basin, however, in order to assess aspects of hydrological variability that the lack of data causes in the studied region. The hydrological series employed correspond to average monthly and yearly flows at stations selected along the main rivers, both due to stability in their gauging stations and to the availability and quality of data for the 1931-1992 period. This period includes the longest series of simultaneous observations for the stations selected. Similar approaches were applied to the series of precipitation. Through basic statistical analysis, and from the annual evolution of flows and precipitation, the study of the relationship between rainfalls in the area and flows at separate hydrological stations (taking also the annual cycle of precipitation and flows into account), nine hydrological areas were detected. From those areas, well separated from each other, the spatial variability for the Rio de la Plata basin was characterized.Variabilité spatiale des débits et des précipitations dans le bassin du Rio de la Plata Résumé Quelques aspects de la variabilité spatiale dans le bassin du Rio de la Plata, en liaison avec la variabilité climatique, ont été analysés à partir de modifications du débit des rivières considéré comme représentatif de la précipitation annuelle. Ces modifications de débit apportent davantage d'information sur la variabilité climatique que les rares données de précipi-tation et de température, à cause de la grande variabilité de ces grandeurs dans l'espace et dans le temps. Les précipitations ont toutefois été utilisées dans la région la plus active du bassin, mais il s'agissait seulement d'apprécier certains aspects de la variabilité hydrologique en raison du manque de données dans la région étudiée. Les séries hydrologiques utilisées sont les moyennes mensuelles et annuelles des stations sélectionnées sur les principales rivières en tenant compte de leur stabilité, de la disponibilité et la qualité des données pour la période

Both (El Niño-southern oscillation ENSO)-scale and near-decadal variations in precipitation and river flow have been noted in southeastern South America. Here we focus on the Uruguay river basin and its subcatchments. Both river flow and precipitation are analysed with singular spectrum analysis in an examination of how the signals of the subcatchments are related to the overall basin signal. The approximate 6 year signal and the 3.5 year ENSO signal are the two statistically significant peaks for the river flow. Both signals are present in all the available river flows, but only in the precipitation of the upper two-thirds of the basin. Precipitation in the lower part of the basin shows positive trends. The ENSO signal is strongly modulated at the secular time scale; we construct a simple sinusoidal model for this modulation.