Hydraulic and morphological characteristics of middle and upper reaches of the Parana ́ River (Argentina and Brazil)

The Parana ́ River basin is a 2,600,000-km2 South American fluvial system, most of which is in Brazil and Argentina. The channel is about 4000 km long, the mean annual discharge is 17,000 m3 s 1, and the annual sediment load is more than 150,000,000 tons. The basin of the Paraguay River, its main tributary, covers about 38 % of the Parana ́ basin. This paper compares the upper and middle channels of the Paraná. Hydraulic, morphological and sedimentological features of the Paraná River upstream and downstream of the confluence with the Paraguay were analyzed in order to evaluate the changes in these variables. The effect of the Paraguay on water and suspended sediment discharges was examined. The Paraguay River contribution explains most of the variation in channel conditions upstream and downstream of the confluence. The channel pattern, however, remains braided. The high bed load of the Parana ́ River in proportion to the total sediment discharge (21 % in the upper course, 25 % in the middle course) determines the similarity in drainage. D 2002 Elsevier Science B.V. All rights reserved