Hydropower is an important renewable energy resource worldwide. However, its development is accompanied with environmental and social drawbacks. Issues of degradation of the environment and climate change can negatively impact hydropower generation. A sustainable hydropower project is possible, but needs proper planning and careful system design to manage the challenges. Well-planned hydropower projects can contribute to supply sustainable energy. An up-to-date knowledge is necessary for energy planners, investors, and other stakeholders to make informed decisions concerning hydropower projects. This is basically a review paper. Apart from using expert knowledge, the authors have also consulted extensively from journals, conference papers, reports, and some documents to get secondary information on the subject. The paper has reviewed the world energy scenario and how hydropower fits in as the solution to the global sustainable energy challenge. Issues of hydropower resource availability, technology, environment and climate change have been also discussed. Hydropower is sensitive to the state of environment, and climate change. With global climate change, though globally the potential is stated to slightly increase, some countries will experience a decrease in potential with increased risks. Adaptation measures are required to sustainably generate hydropower. These are also discussed in the paper. 1. Introduction 1.1. World Energy Scenario and Sustainable Energy In this era, concerns about environment and climate change management influence choices investors and international financing institutions make concerning energy projects . The word “environment” can be defined in many ways depending on the discipline; but it is broadly understood to refer to surroundings that interact with life on earth. The surroundings can be divided into nonliving and living components. The important point concerning environment, according to Gorshkov and Makarieva , is that it provides resources, such as energy, that support life on earth. Since energy is sourced and processed into a usable form from the environment, activities pertaining to its extraction, transportation, conversion, and utilisation impact the environmental system. The impacts are pronounced in thermal energy systems. For fossil fuel energy systems, it is also not possible to totally avoid emissions and environmental setbacks because of combustion. During the combustion process, energy is converted from chemical into heat and the gaseous products of combustion are ejected from the system at a higher
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