evidence: The Orange River is a vast and complex river system located within the Southern African Development Community (SADC). The basin has a size of 964,000 square kilometers, and is inhabited by 19 million people. The river is shared between Lesotho, South Africa, Botswana, and Namibia. It rises in the Lesotho highlands, where it is known as the Senqu River, and then flows 2,300 kilometers towards the Atlantic Ocean. Along the way, it is fed by a number of tributaries, most importantly the Caledon River, Vaal River, Fish River, and Molopo-Nossob River. For the last 600 kilometers before entering the Atlantic Ocean, the lower Orange River runs along the boundary between South Africa and Namibia (Sullivan, 2015).