Transported sediment in the last stretch of the Pilcomayo River: features and trends

ORFEO, O.; IRIONDO, M.

Leeds

Congreso; International Conference on Fluvial Sedimentology; 2013

University of Leeds

During the dry season, the whole mean concentration of suspended sediments was 750 and 1150 mg L-1, at MLP and EMB cross sections, respectively. During the flood those concentrations were 17,000 and 13,000 mg L-1, respectively. The sand concentration was relatively homogeneous during all the studied periods, constituting around 13 to 15% of the total suspended sediments. The remainder constituted the silt fraction. The sediment distribution showed a clear vertical stratification, with the higher values near the channel bottom during all the studied hydrological periods. Sand, silt and clay were recognized in the channel bed, with the silt fraction been the most abundant size (nearly 50% of the total), demonstrating the homogeneity of the provenance area. From the results obtained, a downstream loss of fluvial competence is acceptable, confirming the sedimentation trend in the last portion of the Pilcomayo River. The rate of decline in concentration and its implications of sedimentation rates will be discussed.