ABSTRACT
The East African plateau receives so little rain over most of its plains and valleys that the climate, except at higher altitudes, is in many places critical for agriculture. The Sonjo inhabit one of those regions which are too arid for the cultivation of crops by rainfall alone. The land is well endowed with streams and springs which are favourably located so that their waters can be used for irrigation. The Sonjo make use of this water and are thus enabled to base their subsistence mainly upon crop cultivation. The principal conceptual categories that Julian Steward uses in his study of irrigation societies—formative and florescent periods of development, conquest, militaristic expansion, and the like—are not appropriate concepts to apply in the Sonjo study, which is essentially a synchronic analysis of a small tribal society about which we have little historical information of the kind that Steward uses.
