Water, water everywhere [guest editorial]

This paper discussies the hydropower progress in several regions of the world: South America, where hydro development is very active; the United States and Canada, where the greatest portion of the hydro potential has already been explored; China, a fast-growing market with significant hydro resources; and Africa, with still a large potential unexplored. Each article will cover the state of development of hydroelectricity in its region. Potential for growth, specific projects, environmental constrains, and economics are a few of the issues that will be covered with articles encompassing diverse flavors around the globe.