•These fluvial systems contribute 330km3yr−1 of freshwater into the Caribbean Sea.•From 2000 to 2010 the annual streamflow of these fluvial systems increased up to 65%.•A period of intense hydrological change was detected from 1998 to 2002.•The annual and quasi-decadal bands appear as the main oscillatory components.•ENSO-related band represents a second-order oscillatory component. The monthly averaged freshwater discharge data from ten rivers in northern Colombia (Caribbean alluvial plain) draining into the Caribbean Sea were analysed to quantify the magnitudes, to estimate long-term trends, and to evaluate the variability of discharge patterns. These rivers deliver ∼340.9km3yr−1 of freshwater to the Caribbean Sea. The largest freshwater supply is provided by the Magdalena River, with a mean discharge of 205.1km3yr−1 at Calamar, which is 26% of the total fluvial discharge into this basin. From 2000 to 2010, the annual streamflow of these rivers increased as high as 65%, and upward trends in statistical significance were found for the Mulatos, Canal del Dique, Magdalena, and Fundación Rivers. The concurrence of major oscillation processes and the maximum power of the 3–7year band fluctuation defined a period of intense hydrological activity from approximately 1998–2002. The wavelet spectrum highlighted a change in the variability patterns of fluvial systems between 2000 and 2010 characterised by a shift towards a quasi-decadal process (8–12years) domain. The Intertropical Convergence Zone (ITCZ), El Niño – Southern Oscillation (ENSO) events, and quasi-decadal climate processes are the main factors controlling the fluvial discharge variability of these fluvial systems.