This chapter looks at what the Geniza archives tell us about Cairo’s community’s relationship with the Nile. Since its discovery by scholars in the late nineteenth century, this large and unique corpus of medieval and early modern manuscripts has allowed scholars to access part of the quotidian experience of Cairo’s – and to a wider degree Egypt’s – Jewish communities over centuries. It also documents their integration within transnational and diasporic webs that, just like Egypt’s agricultural surpluses, extended to Palestine and the wider Mediterranean. As is shown, the letters preserved in the Geniza complement, and at times disrupt, literary evidence. They notably do so by evoking a medieval world in which real disaster was perhaps never far away, and where the Nile, its waters, floods and promises or denial of sustenance, were always in view.