Robert F. Gray 
The Sonjo of Tanganyika [PDF ebook] 
An Anthropological Study of an Irrigation-based Society

Originally published in 1963, this was the first monograph concerning an African people in which an irrigation-based society was studied in detail and its implications explored. The Sonjo, a Bantu-speaking people isolated among cattle pastoralists of what was Northern Tanganyika, are remarkable for their complex irrigation system and political organization. The inter-connections between the irrigation system, the religious cult of a culture hero, and the special features of their social organization are at the core of this analysis.