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. Flooding in the Basin The subject of floods is fraught with more drama than that of water shortages, for a flood can be not only a hardship but a catastrophe. For this reason, accounts of floods tend sometimes toward exaggeration, and appeals and proposals for protection against flood threats often take on the highpitched tones of impending disaster. The subject badly needs sober public understanding, despite the fact that for decades a good many knowledgeable scientists and engineers and planners have been laying out their conclusions for general perusal.