At any rate, they are not an answer for Washington's problems. Even if enough of them were installed specifically to provide the storage volume needed for metropolitan use, the question of operation—ensuring and coordinating releases from a large number of places at varying long distance upstream from the point of intended use, in such a way as to make the required volumes of water arrive at the right time, without waste—would be very difficult even with much more sophisticated and expensive design than these structures customarily have. Without it the problem would be insuperable.
Thus, for metropolitan Washington's water in the near reaches of the future, some reservoir storage is indicated with fewer ecological, recreational, and scenic drawbacks than a Potomac main stem dam, and more efficiency for massive supply than the small headwater structures. Since the Potomac river system is a unit, with the metropolis at the downstream end of its non-tidal part, water stored anywhere in the upper Basin can be released for use there. This gives much freedom of choice in the selection of sites for reservoirs and in the combination of releases from various places to make up an adequate total supply, though obviously good management will be needed to coordinate the releases and avoid the waste of water.
It also means, if good principles of river-basin management are followed, that reservoirs to supply water at Washington can be located and designed so as to satisfy major upstream demands at the same time, and that they can be fitted in with regional and Basin needs for water quality improvement, flat water recreation, and in some places flood protection. In such conjunctive planning, based in the Basin's physical unity, commencing now and continuing on into the future as new needs and new ways of satisfying them come to view, lies the main hope of developing the Potomac water resource in such a way as to avoid waste of money, waste of water itself, and waste of the landscape and the general environment. Without it, nothing can result but a piecemeal haggling to bits of the river system as local demands grow acute and local pressures force the adoption of one-shot measures. With it, towns and areas and industries can be guided toward sensible and thrifty action that fits in with the wellbeing of the whole Potomac region—toward buying a share in the water of a rightly designed, rightly placed reservoir large or small, toward development of ground water resources where these are adequate, toward the use of new technology that may be feasible and suitable.
The range of choices is certain to enlarge with time, and the ease with which right choices can be made. In this computer age, mathematical models of river systems, including the Potomac, are at work manipulating hydrological data and quickly indicating optimum coordinated solutions for given water problems that formerly would have taken many weeks to solve, if indeed men could have arrived at such exact solutions at all. Computers are no better than the material that is fed them, however, and the need for new water data—for facts—is acute, if computers and the men who run them and the policy makers to whom they report are to pick the best ways of doing things. So is the need for means of giving "intangible" values their right weight in the whole process. But the computers are the keystone of the new technology and they are going to make right coordination simpler.
With coordination also, as we shall see hereafter, there is the strongest possibility of getting the river system clean again and keeping it that way, and furthermore of vouchsafing some measure of protection to the landscape through which it flows. For the physical unity of a river basin has many implications, and not the least of them is that the people who live there can be guaranteed at least a physical chance to lead full and wholesome lives.
Water supply for upstream areas of the Basin, then, is not a separate thing from water supply for the downstream metropolis and should not be treated as separate. They are all drinking from the same fountain. Where an upstream demand is great enough or is going to be great enough in a short span of years to warrant major storage, that storage must be keyed in with all other demands that it might meet or help to meet, including that at Washington. Where an area of lesser need is shut off by its location from sharing in such major storage, groundwater development or headwater reservoirs may well be the answer, but these measures too should be made to serve as many purposes as may be required for the protection of the area's whole range of interests and the good of the entire Basin. The need for such interweaving—for coordination, for planning and action that are unified—is primary, and will emerge again and again.