region of sandy alkaline clay depressions (pans) in northeastern Botswana. The pans form a broad inland basin that descends gradually from 3,150 feet (960 m) in the west to 2,975 feet (900 m) and then rise more steeply to between 3,500 and 4,000 feet (1,050 and 1,200 m) eastward. They make up the lowest part of the Kalahari (desert), the elevation of which is otherwise fairly uniform (3,000 feet) and which occupies the majority of the area of Botswana. The area was occupied by a great lake at various times in the Pleistocene Epoch. The pans (playa) are flooded in normal rainy seasons by the Boteti (Botletle) River, on the west, which in turn is flooded by the Okavango River, to the north. The Makgadikgadi pans are among the largest in the world, with Ntwetwe Pan measuring approximately 75 miles (120 km) east-west and 100 miles (160 km) northeast-southwest and the smaller Sowa Pan about 45 miles (70 km) wide and 70 miles (110 km) long. In normal weather the pans consist of a series of shallow pools, sandy alkaline clays, and islands of grass and are the habitat of thousands of flamingos. Commercial exploitation of the soda deposits of the region has not been undertaken because of the lack of water supplies and electrical power, although the economic potential of the salt deposits has been fully assessed.