Freshwater discharge into the Caribbean Sea from the rivers of northwestern South America (Colombia): magnitude, variability and recent changes

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Juan Camilo Restrepo, Jorge Pierini, Juan Carlos Ortíz, Kerstin Schrottke, Luís Otero, Julián Aguirre

Wednesday 1 july 2015

12:15 - 12:30h at North America (level 0)

Themes: (T) Extreme events, natural variability and climate change, (ST) Hydrological extremes: floods and droughts

Parallel session: 9I. Extreme events - Flood Drought

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Data of monthly averaged freshwater discharge from ten rivers in northern Colombia (Caribbean alluvial plain), draining into the Caribbean Sea, are analysed to quantify discharge magnitudes, to estimate long-term trends, and to evaluate the variability of discharge patterns. The rivers deliver ~340.9 km3 yr-1 of freshwater to the Caribbean Sea. The largest freshwater supply is provided by the Magdalena River with a mean discharge of 205.1 km3 yr-1 at Calamar. This amounts to 26% of the total fluvial discharge into the Caribbean Sea. From 2000 to 2010, the annual streamflow of these rivers increased to 65%. Upward trends in statistical significance are found for the Mulatos, Canal del Dique, Magdalena, and Fundación Rivers. The concurrence of major oscillation processes and the maximum power of the 3-7 year band fluctuation define a period of intense hydrological activity from approximately 1998 to 2002. The wavelet spectrum highlights a change in the variability patterns of fluvial systems between 2000 and 2010, characterised by a shift towards a quasi-decadal process (8-12 years) 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. Finally, an analysis (20-year moving window) of extreme streamflow data shows that hydrological seasons have changed significantly in the last decades but such changes do not occur in the whole region simultaneously.