Aquatic ecosystems must play a major role to ensure that water, which is both essential and scarce, is always available for both present and future generations. This has become even more urgent in light of the ongoing increase in total world population and predicted changes in the world climate. Since aquatic ecosystems have been damaged at a rate far in excess of both natural restoration and anthropogenic restoration, it is essential that both restorative processes be accelerated. However, ecological disequilibrium, evolutionary processes, and invasive species are likely to disrupt both processes. Most current debate focuses on water distribution; however, since the health of the aquatic ecosystem plays a major role in water quality and availability, it is argued that sustainable use of the planet requires that this attribute be given greater attention. The prospects for fully restoring damaged aquatic ecosystems to predisturbance conditions increasingly appear unlikely. Partial restoration now appears to be a more accurate description of the process, although full ecological restoration should always be an aspiration.