The basin began as a sinking landmass mostly covered by forest and contained many more lakes than now. The climate has changed from wet to arid over the last 60 million years. Most of the rivers in the Lake Eyre basin are now slow flowing, flat and completely dry for lengthy periods. When the country north of the basin floods, floodwaters drain via the main rivers of the basin, Cooper Creek, Georgina River and Diamantina River southwards towards Kati Thanda-Lake Eyre, the country's lowest point at below sea level. The water overflows the river banks, across the floodplains, filling waterholes and wetlands and carving new channels, giving rise to the name Channel Country. Most of the rain which falls in the north never reaches the lake 1,000 km away, which only fills occasionally.