The Rio de la Plata separates Uruguay and Argentina on the southeastern coast of South America. It is the widest estuary in the world, the mouth the estuary is approximately 120 miles wide. At the head of the estuary the width is about 20 miles. The Rio de la Plata originates at the junction of the Uruguay and Parana rivers. The estuary is about 170 miles long and empties into the Atlantic Ocean. The watershed begins in central Brazil. The Rio de la Plata collects waters from rivers that flow in the highlands of Brazil, Northern Argentina, the south of Brazil and Paraguay.

The Rio de la Plata is very important economically to the countries that are within the basin. Harvests from the estuary are the most important resource. The estuary is the main fishing ground for the region. Hydroelectric plants that are found within the estuarine region provide energy to the area. The rivers that flow into the estuary are the main water resource for the most densely populated regions of South America.