Radiocarbon and tritium evidence for direct rain recharge to ground waters in the northern Kalahari

THE Kalahari, a flat and sand-covered region of more than 600,000 km 2 (Fig. 1), has long been classified as a desert because of the virtual absence of surface waters in the form of springs or perennial rivers. The only exception is the inland drainage system in the north, the Okavango delta and Makgadigadi salt pan, which are fed successively by rainwater which drains from the remote highlands of Angola through the Okavango river. © 1974 Nature Publishing Group.