Water Yield from Snow as Affected by Consumptive Water Losses

The snow which accumulates each winter on high elevation forest and rangelands has long been known to be the principal source of the water supply for most of the West. The conservation of that snow resource has become of major concern as demands for more water have grown apace with the needs of an expanding economy. There are several possibilities of meeting the future water needs of the West. One is to build more storage dams and transmountain diversions. We can also tap more of the ground water basins. There is room too for reducing the waste of already developed water supplies by improving our water conveyance systems and by using water more efficiently. In addition, there is the possibility of reducing the consumptive losses of snow water by altering the vegetation on the watershed lands where runoff begins. The idea of reducing evapo-transpiration losses of snow water by watershed management practices is both intriguing and hydrologically sound. There is evidence, however, that the benefits which may accrue from changing the plant cover may be offset by a number of adverse effects. The purpose of this paper is to point out some of those conflicting possibilities in the hope of clarifying the thinking about watershed management problems, especially those within the Intermountain region.