it against the
worst effects of their numbers. In fact, very luckily, it already is
being so manipulated in dozens of ways ranging from methods of farming
and forest management to sewage treatment. It is possible to hope that
present population forecasts may somehow find less than ample
fulfillment, but it is not possible to count on it for planning
purposes. Nor is it possible to wish out of existence situations already
serious.

[Illustration: WATER SUPPLY POTOMAC RIVER, WASH. D.C.]

At times during the hot months of drouthy 1966, the climax of a dry
cycle that had begun to develop five years earlier, the Washington
metropolis was not too far from the bottom of its water barrel. The
situation was not as bad as in some other Northeastern regions, nor as
bad as some local analyses claimed, but it was bad enough. The highest
daily withdrawal of the year was on June 26, when the metropolitan water
intakes in the Potomac sucked out approximately 380 million gallons. Of
this some 30 million gallons had to do with a pumping pattern pertinent
to adjustments within the system, and the other 350 million went for the
use and refreshment of a metropolis afflicted by summer's heat. The
total figure represented less than half of the river's flow at that
time.

[Illustration: GROUND WATER LEVELS WASHINGTON, D.C. AREA]

For a couple of days in September, however, the Potomac's flow reached
an all-time low of about 390 million gallons a day. Even if the demand
on those days had risen as high as in June, which it did not, there
would still have been an excess, but not a very safe one. Heavy storms
shortly thereafter eased the situation, and rainfall since then has
definitely broken the long drought pattern, returning stream and
groundwater levels to normal.

The sober fact is that the Washington metropolis is nearing the point
where its traditional main dependence on the Potomac's free and
fluctuating flow for water supply--with supplementary quantities from
Occoquan Creek, the Patuxent, and a few wells--is not going to work
during prolonged dry periods. Total flow even in a drought year remains
impressive, but dependable daily flow--which is what counts for
supply--varies tremendously.

Other centers of population in the Basin are up against water supply
problems or are going to come up against them shortly. The towns and
industries along the North Branch, around Cumberland and upstream, are
strongly aware of a water need com