Magdalena river: interannual variability (1975–1995) and revised water discharge and sediment load estimates

Abstract

Magdalena river discharges 228 km 3 of water annually, or on the average 7200 m 3 s −1, into the western Caribbean based on 21 years of daily data, 1975–1995. The mean sediment load for the Magdalena is 144×10 6 t yr −1, corresponding to a sediment yield of 560 t km −2 yr −1 for the 257,438 km 2 basin. Magdalena is the largest river discharging directly into the Caribbean Sea, and it has the highest sediment yield of any medium-sized or large river along the entire east coast of South America. Magdalena sediment load is well correlated with water discharge ( R 2=0.76). Regression of water discharge on the Southern Oscillation Index (SOI) shows that 69% of the variability of the Magdalena streamflow is explained by the SOI, with high discharge occurring during La Niña phase and low discharge during El Niño phase. Cross-spectral analysis between Magdalena discharge and the SOI indicates an average recurrence interval of 3.0 years with a coherence, Y 2=0.90, and that the discharge anomaly is in phase with the SOI anomaly. Analysis of time series of sediment load, 1975–1995, indicates that la Niña phase is characterized by a sediment load as high as 1600×10 3 t day −1. Sediment load is also correlated with SOI with a coefficient of variation of R 2=0.54. Clearly, the Magdalena water discharge and sediment load are strongly coupled to the El Niño–La Niña cycle.