The Sonjo (native name Batemi) are a people living in northern Tanzania, 30-40 miles west of Lake Natron, who have lived for centuries as an isolated enclave in Maasai territory. In 2002 the Sonjo population was estimated to number 30,000 (Ethnologue). They are known for their use of a traditional irrigation system in farming, a practice which has led some historians to link them to the hitherto unexplained ruined irrigation systems of Engaruka, 60 miles to the southeast. The term Sonjo is the name given to the people by the Maasai; they call themselves Batemi and their language Ketemi or Gitemi.