Water projects may have ecological impacts in great diversity—in the area of impoundment; downstream from there; in delta, bay, or ocean areas; and in distant areas of water use, either agricultural or urban. Examples of several kinds of impacts are presented, emphasizing those occurring in California. Recognition of the ecological impacts of water projects by individuals depends on where they live and how they are affected by the proposed project. Concerns with environmental impacts presently shown by many individuals and groups are expected to have lasting effects on water-project planning, construction, and operations. Developing water while protecting the environment will require greater objectivity by and cooperation between engineers, ecologists, sociologists, politicians, special-interest groups, and others, as well as greater willingness to deal with complexities.