Once upon a time the river systems in East Africa were linked to the Congo basin - thus rivers flowed from east to west. However, tectonic earth movements resulting in the eastern and western rift valley formation caused the reversal of the drainage system to collect in a shallow basin that became Lake Victoria, a source of fresh water, livelihood and marine life. However, over the recent years, especially from 2003, there has been a marked drop in the water level. At some points the receding shoreline is prominent. Most conspicuous is at the source of River Nile, where the once old water works concrete slabs are sticking out. Several years ago they were submerged by about a metre or two, according to Sunday Vision.