Several of the enormous rivers of South Asia ─ from the sprawling Indus system in the West to the volatile distributaries of the Ganges in the East ─ were turned into modern rivers through the course of British colonial rule in the nineteenth century. This ‘Great Hydraulic Transition’, I argue, was philosophically premised on the need to cleave land and water into two distinct non-overlapping natural domains. Rivers, hence, were quantified as units of flow, disclosed by comprehensive control and harnessed as a resource with weirs, embankments and dams, while land became the source of ownership, permanent property and colonial law.