The world has a multitude of reservoirs. Usually, and properly, the dams which retain the water were built with immense caution. Their designers were especially worried about dam failures, floods and water pollution. Today, there is less to fear. Hydrological and structural monitoring give advance warning of floods and faults; filtration equipment removes pollution. These changes have made existing reservoirs into potentially rich places for landscape development. Future reservoirs can be developed as multi-functional projects for wildlife, swimming, boating, fishing, waterside building, power generation, irrigation, river regulation, scenic enhancement and, occasionally, great works of art. Existing reservoirs should be assessed and made subject to EID. They are capable of yielding more private and public goods than they do at present.