evidence: The Orange River (Gariep River, Groote River, or Senqu River) is the longest river in South Africa. It rises in the Drakensberg mountains in Lesotho and then flows west through South Africa to the Atlantic Ocean. The river forms part of the international borders between South Africa and Namibia and between South Africa and Lesotho, as well as several provincial borders within South Africa. Although the river does not pass through any major cities, it plays an important role in the South African economy by providing water for irrigation, mining, industrial and municipal use, as well as hydroelectric power. The Vaal River basin, part of the broader Orange River basin, is the industrial heartland of South Africa, producing more than 25 percent of the country's gross domestic product (GDP). [...] The total catchment of the Orange River (including the Vaal) extends over 973,000 square kilometers, i.e., about 77 percent of the land area of South Africa. Approximately 366,000 square kilometers (38 percent) is situated in Lesotho, Botswana, and Namibia. The Orange River provides a belt of green vegetation through an otherwise hot and dry desert. It also provides water to the Orange River mouth, which is used by many birds as they migrate from one hemisphere to another annually. South Africa became a signatory to the Convention on Wetlands of International Importance in 1971. It must therefore identify and protect areas of environmental importance with respect to wetlands used by waterfowl.