The assessment and management of the environmental and social impacts and issues of hydropower projects are vital to their sustainability, and are necessary from the earliest concept stages of a hydropower project, during its preparation and construction, and through its ongoing operation. Environmental and social impact assessment (ESIA) of a project in its design or preparation stage is universally practised. It is a legal and permitting necessity, and is used to identify risks for the project or the business, and to meet the requirements of stakeholders such as lenders and the public. While ESIA has become widely established, there is an increasing focus on (1) avoiding adverse impacts, by the strategic planning of one or more projects across a wider area; on (2) social and health impacts; and on (3) systematic and adaptive management, through the use of environmental and social management systems.