s 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.

Far out, though possibly not very far off in time, is the likelihood
that future water planners will be able to count on some degree of
control over a given region's rainfall and snow. Through
experimentation, this subject is rapidly being excised from the mists of
superstition that once surrounded it, and the Department of the Interior
has an active program of research and study in the West, with tremendous
implications. But, yet again, present planning cannot take it into
account except in the sense that, along with some of the other
technologies already mentioned and undoubtedly others that have not yet
even emerged to view, it adds to the near certainty that future planners
are going to have a much wider range of alternative methods at their
disposal, to choose from and mix as may seem best. And this, in turn,
reemphasizes the wisdom of flexibility in present planning and the need
to keep big irreversible decisions to a minimum.

The upper Potomac estuary from Little Falls down to the vicinity of
Marshall Hall and Mount Vernon or below contains a great deal of fresh
water, an accumulation made up of inflow