Scholarship on nineteenth-century Ottoman hydraulic works in Iraq tends to focus on the particular challenges posed by the construction of the Hindiyya barrage on the middle Euphrates in the province of Baghdad. To be sure, there is good reason for such a focus: up until William Willcock’s design for a new Hindiyya barrage during the early twentieth century, excessive amounts of the Euphrates’ waters entering the Hindiyya canal and changing the main channel of the middle Euphrates constituted one of the most difficult environmental problems in the administration of Ottoman Baghdad during the nineteenth century. Nevertheless, without denying the significance of the Hindiyya barrage in the environmental history of Ottoman Iraq, this paper suggests that such a narrow focus obscures much more than it reveals as it overlooks not only the diversity of the profile of nineteenth-century Ottoman hydraulic works on both the Tigris and the Euphrates rivers, but also what Ottoman attempts to manage these two rivers can reveal about the nature of Ottoman modernization efforts in Iraq during the nineteenth century. Drawing on Ottoman, British, and French archival records, this paper highlights lesser-known nineteenth-century Ottoman hydraulic works on the Tigris and Euphrates rivers, focusing particularly on those portions of the rivers running through the Ottoman provinces of Baghdad and Basra. It offers examples of state-tribal cooperation in a region of the Ottoman Empire in which scholars have often emphasized the contentious relationship between both groups, while at the same time offering examples of sanitary concerns (such as frequent outbreaks of cholera) as an impetus for improved water management in a region of the Ottoman Empire in which scholars are just now beginning to consider the importance of microbes in the writing of history. In so doing, this paper not only demonstrates the centrality of careful water management to Ottoman administration of Baghdad and Basra, but also the importance of environmental concerns in general to Ottoman modernization efforts of the nineteenth century.