 It also roughly coincides with the start of the diminishment of the Engaruka River's flow as well as those of other streams descending from the Ngorongoro highlands; water sources around which Engaruka's irrigation practices were centered.According to the Maasai Nilotes, who are the present-day occupants of Engaruka, the Iraqw also already inhabited the site when their own ancestors first entered the region during the 18th century.In 2001, the Iraqw population was estimated to number around 462,000 individuals.