This book maintains that water and waterscapes are holders of relational value, which contribute to enhancing human capabilities. From a strong sustainability perspective and under the Habermasian framework on Discourse Ethics, a Universe of Discourses in water-related practical problems is established in terms of four ethical nexuses, including the water-human-sufficiency nexus, the water-production/consumption nexus, the water-energy-climate nexus, and the waterscapes nexus. An ethics in sustainable water use is then established, and placed in the case of China in general and the Heihe River Basin (HRB) in Northwest China in particular.