Doubling of the amount of impounded waters in California is in the foreseeable future. Basic climatology dictates winter and spring storage and summer and fall drawdowns, a feature common to far western impoundments. Most of these impoundments will support warm-water fisheries. Native fresh-water fish populations in California and the lower Colorado River have not adjusted to the combination of impoundment and predation by introduced warm-water sport species and often the introduced species have not maintained desirable population structures. The sunfishes frequently stunt and are believed to depress the bass populations. Extremely poor survival of bass-of-the-year is common. An unsatisfactory bass-of-the-year/forage ratio exists in the fall when the young bass turn to a fish diet. Food production is poor in the littoral zone because of water level fluctuation, but plankton production in open waters is usually adequate.