The availability of potable water has become an environmental issue, and this reference for the elementary student discusses how rivers may be harnessed with dams and controlled with levees. The book is beautifully illustrated with color photos and one graphic illustration. The appendixes include a two-page glossary and a two-page bibliography of print and Web sites. While mostly about the U.S., brief mention is made of the Three Gorges Dam built in China. A very brief if colorful introduction.