Water is one of the most valuable natural resources for humankind and other forms of life on earth, and this chapter addresses the topic of its conservation. Environmental psychology (EP) investigates the dispositional and contextual factors that incite both water waste/contamination and conservation. It also studies the psychological positive consequences that result from engaging in water conservationist practices. The obtained information has let us know the individual characteristics that promote water conservation behaviors, the extrinsic and intrinsic consequences that maintain those behaviors, and the situations that make people use water in a sustainable way. EP also participates in the design of interventional strategies aimed at the instauration of conservationist uses of freshwater, including water conservation campaigns, environmental education programs, and experiments intended to shift wasteful and contaminating water uses toward more sustainable water-consuming behaviors. A model integrating the knowledge on freshwater conservation determinants and its consequences is presented and future directions for research and interventions are outlined.