The lack of development also presents planners with a fairly clean slate on which to write. In terms of water, few massive human mistakes confront them except the pollution of the upper estuary and certain other reaches like the afflicted North Branch. Therefore they can begin more or less from scratch and can usually find various choices for action against the water problems of the Basin--against pollution, against flood damages, and against impending or existing shortages of water for municipal and industrial use. [Illustration] Though for clarity in discussion we need to classify these various kinds of problems separately, in practice they do not so neatly divide from one another. Nor do they divide from the way the land in the Basin is used or from the pleasure and fulfillment people find in the outdoors. If a region's use of a stream's water is heavy in a dry August, for instance, whatever pollution the stream gets below towns and factories will be more concentrated and damaging than if the stream were flowing well. Pollution itself can affect the utility of water as well as people's enjoyment of it in a stream. A creek watershed that has been ignorantly farmed or roughly assaulted with bulldozers for urban development is an eyesore of erosive destruction, unproductive of crops, wildlife, or poetic appreciation, and can cause both heavier stream flooding in time of storm and lower flow in time of drought by the way its disruption alters the normal behavior of rainwater. The silt that storms wash off of it is not only a major ugly pollutant of flowing water below that point but can complicate flooding and bank-cutting and navigation and other things by settling out into bars and shoals in still stretches, including reservoirs. All of these things, and others as well, have to be considered together as parts of a whole problem. And that problem is that men's hugely increasing numbers and their multiplying technological power over their environment have made it necessary to readjust the balances somewhat in great natural units like river basins--to restore, manage, and protect them in such a way as to be able to hand them over decent and whole and useful to the people who come after. Problems of Water Supply in the Potomac Basin