The other main difficulty has to do with the fact that river water has many uses, which augmentation may enhance or even stimulate. Water released from above during dry periods to increase and steady the river's flow and to help it handle wastes may also help navigation and hydroelectric power generation downstream, though neither of these is any longer a main factor in the flowing Potomac. Augmentation of flow can make the river prettier and more useful for recreation, and it can have stout beneficial effects on fish and wildlife. And under present conditions it constitutes a large increase in water of improved quality for free use by irrigators and industries and municipalities, which may so burgeon as a result that increased water consumption and waste production will cancel out the water quality effects of the reservoir releases in short order. The need here, of course, is for some agency that can solidly guarantee that water released for quality control will be allowed to achieve that purpose and not be diverted to other uses that conflict with it. Where a river runs within a single State, and the State's constitution permits, the State may be able to adjust its powers of control and provide the guarantee. But where more than one State is involved, as on all the main rivers of the Potomac Basin, a good forceful river basin agency is clearly needed to coordinate water supply with water demand, and to ensure that benefits and cost responsibilities of any necessary reservoirs are meted out where they belong. In terms of legal and institutional machinery, in fact, such a river basin agency is the most basic and urgent unfulfilled need along the Potomac, for the coordination and continuing supervision of water management in all its phases--assurance of supply, flood protection, quality improvement, recreation--in the vast physical unit of land drained by the river. And because land's condition is so often influential on the quality and utility of water, the agency's concern and authority must encompass some fundamental matters of land use as well.