If a development cannot satisfy at least two of the three mentioned aspects, it cannot be categorized anywhere in this definition. If a development project can satisfy the environmental aspects but fails one of the social or economic aspects, the development could still be bearable or viable, respectively.

If a project satisfies the economic and social aspects but fails to satisfy the environmental aspects, it is categorized as equitable. In 1979 René Passet proposed a three-sphere framework for sustainable development projects ( Figure 1) According to this framework, development can be considered as sustainable only if it simultaneously has positive social, environmental, and economic impacts. This review outlines the characteristics of ASTs, then discusses and analyzes how they could benefit the sustainability of hydropower development. ASTs can often be retrofit to existing unpowered dams or weirs, providing new hydropower capacity for very little marginal environmental impact. An AST may also reduce the disturbance of natural sedimentation and erosion processes and have smaller impacts on fish and other fauna. At many low head sites, ASTs may be more cost-effective, with lower installation and operating costs than alternative hydropower systems. ASTs increase the number of suitable sites where it is possible to develop sustainable hydropower, including in undeveloped, hard to access regions and small communities. Archimedes screws can operate in low water heads (less than about 5 m) and a range of flow rates with practical efficiencies of 60% to 80% and can generate up to 355 kW of power.

However, in terms of sustainable development, ASTs can offer many economic, social, and environmental advantages that make them an important option for providing sustainable hydropower development. As with other energy solutions, ASTs are not a global solution for all situations.

ASTs offer a clean and renewable source of energy and are safer for wildlife and especially fish than other hydro generation options. Archimedes Screws Turbines (ASTs) are a new form of small hydroelectric powerplant that can be applied even in low head sites.

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