<P> The Orange rises in the Drakensberg mountains along the border between South Africa and Lesotho, about 193 km (120 mi) west of the Indian Ocean and at an altitude of over 3,000 m . The extremity of the Orange River inside Lesotho is known as the Senqu . Parts of the Senqu River freeze in winter because of the high altitude there . This creates droughts downstream of it which mainly affect goat and cattle production . </P> <P> The Orande River then runs westward through South Africa, forming the south - western boundary of the Free State province . In this section the river flows first into the Gariep Dam (the largest in the country), and later into the Vanderkloof Dam . From the border of Lesotho to below the Van der Kloof Dam the river bed is deeply incised . Further downstream the land is flatter, and the river is used extensively for irrigation . </P> <P> At the western point of the Free State, southwest of Kimberley, the Orange meets with its main tributary, the Vaal River, which itself forms much of the northern border of the province . From here the river flows further westward through the arid wilderness of the southern Kalahari region and Namaqualand in the Northern Cape Province to meet with Namibia at the 20th degree of east longitude . From here it flows westward for 550 km, forming the international border between the province and Namibia's ǁKaras Region . On the border, the river passes the town of Vioolsdrif, the main border post between South Africa and Namibia . </P> <P> In the last 800 km (500 mi) of its course the Orange receives many intermittent streams and several large wadis lead into it . In this section, the Namib Desert terminates on the north bank of the river, so under normal circumstances the volume of water added by these tributaries is negligible . Here the bed of the river is once again deeply incised . The Augrabies Falls are located on this section of the Orange, where the river descends 122 m (400 ft) in a course of 26 km (16 mi). </P>

Where does the orange river and vaal river meet