evidence: The Orange River, is one of Namibia’s major rivers, it rises in the Drakensberg in Lesotho, where it is known as the Senqu River. From where the river leaves Lesotho, it flows westward for some 2200km to where it finally flows into the Atlantic Ocean at Oranjemund. At the source of the Orange River the rain fall is approximately 2000mm per annum and decreases as the river flows westward. At its mouth the rainfall is less than 50 mm per annum. Evaporation, on the other hand, increases in a westerly direction. The total catchment of the Orange River extends over 973 000 square km, however is situated mostly outside the country in Lesotho and Botswana. Eskom of South Africa operates hydro-electric power-stations at both the Gariep and the Vanderkloof Dams. The hydro-electric power station at the Vanderkloof Dam was the first power-generation station in South Africa situated entirely underground.