The river has two large dams : the Manantali Dam in Mali , and the Maka-Diama Dam on the Mauritania-Senegal border , near the sea . The river has two large dams along its course , the Manantali Dam in Mali , built as a reservoir , and the Maka-Diama dam on the Mauritania-Senegal border , near the outlet to the sea , preventing access of salt water upstream .