falhas de identificação e autenticação. Text 3A4 During the last century water infrastructure projects involving large dams played a major role in the socio-economic transformation of many countries. At the same time, in a significant number of cases the benefits were not shared equitably, and the negative impacts on the environmental and sociocultural structures were excessive. In some cases their economic performance was questionable. Diverging views have arisen on the merits and demerits of dams, the roles they play, and their alternatives in providing water and energy services. However, recognition that such roles are complementary rather than mutually exclusive has been growing as the dam debate has moved forward. It is envisaged that, as part of the global effort to improve water and energy supplies, more dams will be constructed, especially in developing countries, alongside other diverse alternatives. There will, consequently, be a need to enhance the benefits of dams and avoid many of their drawbacks by applying better decision-making processes within the overall framework of sustainability. There are complex issues around the planning and management of dams in the context of sustainable development which will need to be adequately considered and addressed to achieve sustainable outcomes. Dealing with the environmental and social challenges within the context of meeting water and energy needs is at the heart of the sustainability of projects involving dams. Dams are one of the options, structural or non-structural, available to meet specific water or energy needs. In many cases water and energy services are best provided through a mix of options. Each case is different. A decision to build a dam should emerge after a comprehensive assessment of the full range of available options, giving appropriate consideration to all aspects of sustainability. United Nations Environmental Programme. Dams and Development: Relevant Practices for Improved Decision-making. Nairobi: The Secretariat of the Dams and Development Project, 2007. p. 10-1 (adapted).