One of the principal objectives of Integrated Water Resources Management (IWRM) is to solve water and development problems using methods that are environmentally sustainable, socially equitable, and efficient. In this chapter, we demonstrate how the principles of citizen science—the intrinsic involvement of nonscientist local stakeholders throughout the entire life cycle of a project—have the potential to complement and benefit those of IWRM; in particular, in relation to creating scientific evidence that underpins the governance of water resources. The rapid, recent development of information and communication technologies such as the Internet, smartphones, and social media has already demonstrated their capacity to make knowledge creation and governance more multidirectional, decentralized, diverse, and inclusive. We show how such new technologies can be harnessed with a citizen science approach to interrogate different aspects of the water cycle. One particularly promising development is to support citizen science with robust and low-cost sensor and networking technology. Such networks offer not only improved data coverage (especially in remote or data-scarce regions) but also enhanced sustainability at a time when monitoring networks are in decline globally. We argue that, in certain cases, citizen science and polycentric governance approaches can enrich and complement IWRM and merit greater attention.