This chapter reviews the spread of irrigation technology across the Sahara in antiquity, and its effects on settlement agriculture and the movement of people. Recent work has stressed the close connections between the introduction of foggara technology and the rise of Garamantian civilisation, which featured intensive agriculture and incipient urbanism. However, many oases achieved substantial size through the use of well technologies, artesian springs or a combination of technologies. Another key question relates to the effects of the eventual decline and failure of these irrigation systems in terms of population movement and fragmentation of states such as the Garamantes. After presenting new AMS dating evidence for Garamantian foggaras, the chapter advances the discussion by examining the wider picture of foggara distribution within a survey of the evidence of irrigation technologies across the Sahara and whether and to what extent the distribution of foggaras beyond the core Garamantian heartlands might be seen as an indication of Garamantian control or influence. It explores what foggaras, wells and new crop introductions might suggest about agricultural intensification and organisation. This has implications for assessing agricultural intensification in the ancient Sahara. Finally, it considers causes and possible effects of irrigation failure and in some cases collapse.