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

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

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.