Going outside the Basin for any significant part of the metropolitan water supply does not appear to be justified. Some water is presently being drawn from impoundments on the Patuxent just north of the city, but no more of it can be counted on. Diversion from the voluminous Susquehanna much farther north is feasible from an engineering standpoint. But the cost of it would be relatively high, and there are also certain strong objections in principle, based on the facts that the Potomac does have plenty of water and there is no inherent moral advantage in transferring the question of development elsewhere, that the Susquehanna Basin may well need its own water at some future time, and that the ecological effects of such diversion on the immensely valuable fisheries of Chesapeake Bay, which are dependent in large part on a shifting balance of salinities maintained by the tributary rivers, are unclear. "Planned scarcity" of water in a community, wherein administrators and public alike accept the certainty that during dry times lawns and parks and golf courses and sometimes human skins will have to do without the application of water for a spell, is a reality of life in some arid regions and is probably always going to be. Elsewhere it is, or should be, an element in the design planning of industries that use heavy quantities of water for cooling and such processes. All water supply planning must consider it, for to build against any conceivable shortage would be prohibitively expensive. Pricing of water so as to cut down on waste without curtailing ample legitimate use may well be a longrun tool, as has been suggested. But in terms of general municipal and industrial water, any great degree of calculated shortage hardly seems appropriate for a humid-zone city which has a fine river at its doorstep and happens also to be the national capital, so that a scarcity would be of national concern in a number of ways. Federally established and maintained parks and open spaces, for instance, with their carefully tended vegetation, would be one of the first things to suffer. Desalting of sea water, another reality now in arid zones and one of immense importance, has a certain degree of planned scarcity built into it by way of its price, at least at present. Some people believe that in time this process will be refined to the point that it can furnish abundant cheap water to all the world's seacoast cities. Certainly as it develops it may well have a potential for marginal drought-proofing at Washington, an emergency source to be drawn upon if needed. But the day seems distant when it will be truly competitive in price with riverine sources in regions of adequate rainfall.