Bilan annuel et variations saisonnières des flux particulaires du Congo à Brazzaville et de l'Oubangui à Bangui

The suspended load of the Congo and Ubangui Rivers

ORSTOM, Montpellier

Abstract

The suspended load of the Congo and Ubangui Rivers The Congo is the second world major River after the Amazon (mean discharge: 41 000 l³ s^-1, area 3.7 10⁶ km²). A large scientific program in the Congo basin follows the fluctuations of the suspended and dissolved matter fluxes and would characterize the mechanical and biogeochimical erosion with hydroclimatological regimes in the equatorial ecosystems. Measurements are made on the Congo at Brazzaville and Ubangui at Bangui (major northern tributary). The estimate of the suspended load is based on a large and representative sampling. The first measurements (1987) give a sediment discharge to 31 10⁶ tons year^-1 for Congo, 2,9 10⁶ tons year^-1 for Ubangui (respectively 30 and 43% of matter discharge). Mechanical erosion rate is respectively 8,9 and 6 tons km^-1 year^-1. Concentrations are included between 15 and 30 mh l^-1 for Congo, 3 and 55 mg l^-1 for Ubangui. These values are lower than precedent published results of Congo and very small compared with Amazon (11% for erosion rate, 5% for sediment discharge).