Inland arid regions and perhaps other places as well are undoubtedly going to find one answer to water shortages in the recirculation of their treated waste waters through municipal systems. In one form or another such recirculation is already working at certain places in the United States on an emergency basis, and its full potential for industrial use has yet to be explored. However, the indications are that towns' and cities' reliance on it during anything but temporary emergency conditions is going to depend on expensive methods of refinement and "fail-safe" overdesign, plus dilution with new water, which means again that it will probably not be competitive in price with natural water where enough good natural water can be had. To this may be added the observation that the consuming public presently has a few definite lingering qualms about the idea involved, particularly if there is other water around. The underground rocks and sands of the Basin hold huge reserves of water with a fundamental relationship to the whole river system, whose basic dependable sources lie in these aquifers' outflow to the surface. Around the metropolis, some ground water is being taken from wells even now to supplement the overall supply and to satisfy the whole demand of any number of outlying communities. Though locally available quantities are limited and pumping costs rather high, such wells will undoubtedly be highly useful for future extensions of the metropolis, especially into the Coastal Plain. There is also much promise in studies of the Basin's aquifers being carried out by the U.S. Geological Survey to determine detailed patterns of their contribution of water to the stream system and to see if it can be regulated and made even more useful. Such a possibility has great implications in terms of augmenting river flows both for water quality control and water supply, and could mean much at Washington. So could certain techniques of deliberate drawdown of aquifers to induce recharge with excess surface waters or sometimes treated sewage effluent, also presently under study. Ground water as a source has some unique advantages--among them a minimum of evaporation loss, less need for surface structures, and protection against catastrophic contamination--and it deserves full exploration, though it cannot at present be counted on as a significant part of the answer for the metropolis.