This image, taken in February 1984, shows the confluence of the Parana and Paraguay Rivers northeast of the town of Corrientes, in Argentina. The Parana is South America's second largest river (the Amazon being the largest), and the river and its tributaries are important transportation routes for landlocked cities in Argentina, Paraguay, Bolivia and Brazil. Both the Parana and Paraguay Rivers are loaded with sediment; the Paraguay (left) contains a tan sediment and the Parana (right) contains a reddish-brown muddy sediment. As the two rivers merge in the center of the photo and begin to flow southwest, we see how their sediments remain fairly unmixed for many miles downstream. Original high-resolution image here.