ed to points well beyond
the limits of the upper estuary, use of its water for periods beyond a
few days of emergency would become essentially a form of recirculation
of waste waters--with, at this time, the main drawbacks that we noted in
regard to that process and certain others besides. For, under the
low-flow conditions that would bring about its use, the effluents in the
river below the mouth of the Anacostia would penetrate upstream as water
was pulled out below the falls and would reach the pumps in fairly short
order, probably moving in a tongue up the main channel.

With the radical improvement in the functioning of the metropolitan
treatment plants that must be achieved, and other measures to relieve
pollution in this part of the river, valid objections to such
recirculation will of course weaken and ultimately disappear. But no
one can reasonably expect that these things are not going to take a
certain amount of time--quite conceivably enough time to run the city up
against an emergency it could not handle without other, more standard
sources of auxiliary water. Besides the matter of consolidating and
improving treatment of collectible wastes, there are certain other
diffuse and stubborn sources of pollution, as will be seen, for which
good counter measures simply do not yet exist--among them are surface
runoff during local storms and overflow from combined sewer systems.

If the collectible wastes were diverted out of the upper estuary and if
it proved possible to cope quickly with other pollution or to ignore it,
during prolonged use salt water penetration from downstream would take
place as fresh water was withdrawn above and not replaced. Studies on a
mathematical model of the estuary indicate that under conditions that
could materialize, this would make the water at the intake too salty for
use. A barrier dam across the entire estuary at one or another point in
the freshwater section could prevent such penetration, but would be
hugely expensive and undoubtedly more obtrusive on a much-used part of
the riverscape than most upstream reservoirs could possibly be.

Furthermore, even if all these doubts and areas of ignorance were to be
easily resolved, insistence that the upper estuary is the only logical
answer to metropolitan Washington's water problem ignores the fact that
major water demands are building fast in certain already-mentioned areas
of the upper Basin, and that, since the Basin is a hydrologi