Outlines the role of science in restoring or otherwise altering unwanted downstream effects of dams, including eroding river banks, changes in waterfowl habitat, threats to safe recreational use, and the loss of river sand bars, examining seven selected areas of the country -- the upper Salt River in central Arizona; the Snake River in Idaho, Oregon and Washington; the Rio Grande in New Mexico and Texas; the Chattahoochee River in Georgia; the Platte River in Wyoming, Colorado and Nebraska; the Green River in Utah; and the Colorado River in Arizona -- to focus on specific downstream effects of dams and the management issues related to their operation.