In terms of metropolitan Washington's water supply, considered apart from other Basin water problems, the best reservoir site by far in the whole Potomac drainage would be the old River Bend site or the one proposed in 1963 at Seneca, both just upstream from the Falls above the metropolis. In one package, either of them would impound enough water to take care of any likely municipal and industrial demands of the metropolitan region for more than a half-century, besides trapping most silt from upstream to keep it out of the estuary, and providing a good measure of protection for flood-susceptible metropolitan shores. Furthermore, the proximity of such a reservoir to the city would ensure a great deal of aquatic recreation for people there and would somewhat simplify water management problems.
Thus, it is natural that Seneca, the latter proposal of the two, has found strong champions among metropolitan administrators, water engineers, and planners whose thinking has to be primarily in terms of sure and efficient water supply and flood protection. It has found equally strong opponents, however, enough of them to have stalled it to date. It is not yet dead, for it emerges in each new discussion of the city's water situation. It will not be dead until the metropolitan water problem, short-term and long-term both, has found a full satisfactory solution in other terms.
Our feeling remains unchanged since the publication of our Interim Report: that when all factors are weighed and future uncertainties are taken into account, Seneca should not be built at this time. If the price in money would not be high in relation to immediate "market" advantages gained, the permanent price, in river and countryside and those other intangibles that are getting to have more and more weight in men's minds year by year, would be heavy.
The full main stem Potomac, carrying the water from the combined North and South Branches and the Shenandoah and the other upper tributaries down through the Blue Ridge water gap and across the rolling Piedmont and the Fall Line, is at its most typical in the 39 miles from Harpers Ferry to Great Falls. Seneca as originally proposed would inundate 35 miles of this stretch, together with islands and bottomlands, forests of big hardwoods, meadows and productive fields, and that much-used segment of the publicly owned C. & O. Canal, with the trail along its wooded towpath. Even reduced in size and designed as strictly a water supply structure, it would have many of the same effects. There is special and tranquil beauty in this piece of the river, which makes a fine float trip and is much fished, as well as a lot of historical significance dating back to the Senecas and the Piscataways and before. Here these things are not forgotten and removed from men's reach but are available to metropolitans who go to the trouble to seek them out, as many do. Nor is there anything else around to take their exact or even approximate place if they were gone.
It has been pointed out that if the metropolis grows according to predictions, a major part of that growth is going to be upriver, and the main stem of the Potomac will have the same relationship to the metropolis of the future that Rock Creek has to the Washington of today. Thus the decision that is made about the main stem in our generation is similar to the decision that planners had to make about Rock Creek three-quarters of a century or more ago. Those planners decided magnificently well, bequeathing to the future an urban stream and park unique in this country and perhaps the world, a treasure that the public is presently defending against other, newer, subtler threats than mere damming or encroachment.
A reservoir above Seneca clearly could not mean that sort of thing. It would be a useful lake, but devoid of the changeless tone of the Potomac as it flows there now. The reservoir's proper functioning would require fluctuations in its level, with occasional ugliness at the shoreline, and if it would permit a great deal of happy water-skiing and flat-water fishing, the same opportunities are going to be available to Washingtonians in the nearby estuary when it is suitably cleaned up, even though the section immediately adjacent to the metropolis may take a good while to bring up to swimming standards.
In terms of the overall good of the people of the metropolis and the Basin and the country, the water situation at Washington now and during the near future hardly bears a desperate enough aspect to warrant the sacrifice of much of the main flowing river to a reservoir which, like the freshwater estuary, could not be meshed with upstream needs but would serve only the urban areas at and below the Fall Line. Conceivably at some future time, if technology should renege on its promise to bring forth good new alternatives, and population pressures continue to grow, the city may badly need a reservoir there. It is a uniquely valuable site. For that reason, we repeat our Interim proposal that the reservoir site, minimally defined, be preserved against the mass encroachment with which it is imminently threatened, and be utilized principally as part of a major park complex protecting the river and its shores. To defer irreversible decisions and to leave them as much as possible to future generations whose conditions of life and desires we cannot predict with accuracy, can be a principal way of maintaining freedom of choice.
In the category of reservoirs, at the other end of the spectrum are the comparatively small headwater dams that the Soil Conservation Service has been designing and supervising for three decades in authorized watersheds throughout the country. These structures can serve several functions and can furnish for small watershed areas and small centers of population many of the benefits that the Corps of Engineers and Bureau of Reclamation dams furnish for large areas. On their own scale, they are vulnerable to some of the same objections that are aimed at large reservoirs. But the scale is smaller; they tend to be less imposing and pre-emptive of good land than big river dams, "catch the water where it falls" to hold it for local use and to alleviate local flooding, and are backed up by erosion control practices in a program that has proved to be one of the best available stimulants to good land use. For these reasons they have appeal for many rural people and conservationists.
However, the conclusion which some of their supporters have reached is that if only enough of the small dams could be built throughout the headwater areas of a river basin, they would eliminate the need for most other forms of water management, leveling out flood and drought flows and holding a great aggregate amount of water on tap for use anywhere down the line. At times in the past, the controversy between supporters of big dams and supporters of little dams achieved the proportions of a bloodless war, but after a good many years of testing and observation it is now generally agreed by hydrologists that both have their place and that the most appropriate focus for the small dams' functioning is local.