The sad situation of the smaller and much less industrialized Monocacy in the same summer underscores the point. The Monocacy flows through similar farming country and passes by a few towns. The largest of these is Frederick, Maryland, for whose approximately 40,000 people the little river furnishes water and a conduit to carry away the effluent from their average-to-good secondary plant. At times during that dry summer practically the entire flow of the river below Frederick consisted of effluent, with effects on stream life, esthetics, and the general surroundings that are not hard to imagine. Another good example of a place where, under present conditions, augmentation could sometimes be used beneficially is at Great Falls and in the Potomac gorge below. Heavy public expenditure has protected the shore in much of this neighborhood and provided pleasant recreation areas whose main scenic focus is the violent magnificence of the river in its plunge. But the magnificence becomes a rather drab joke in dry summers when metropolitan withdrawals of water above that point shrink the river to a semblance of normal flow. [Illustration: Low Flow Augmentation] The North Branch and some smaller Basin streams also need this same kind of help and most will continue to need it even when the best economically feasible treatment of all collectable wastes entering them is ensured. It can be provided out of reservoirs, large or small, whose need for other purposes as well will keep the cost of dilution within reason. A future possibility, if research presently going on in the Basin verifies it and shows ways of putting it to use, is to employ ground water in the same way. There can be no doubt that if the flowing waters of the Basin are to be put back in good condition and kept that way under population pressures that are in prospect, flow augmentation in some places is going to be an important tool. In the upper estuary, however, its usefulness appears to be far more limited. The plan proposed in the _Army Report_ of 1963, in line with a Public Health Service approach emphasized in the 1961 Water Pollution Control Act, was designed to provide an eventual minimum flow into the upper estuary of 3100 cubic feet per second, or around two billion gallons per day, for the purpose of dealing with treatment-plant effluents and miscellaneous pollution. But more recent investigations have raised strong doubt as to whether such augmentation could do the job in the estuary with its huge volume of water, and its slow, tide-baffled currents that greatly lessen its assimilative capacity.