Snow as an Environmental Factor in the West

SNOW AS AN ENVIRONMENTAL FACTOR IN THE WEST* Phil E. Church University of Washington, Seattle IT IS not necessary for me to remind geographers of the various factors of the physical environment. All recall that climate is one of them, and that climate is judged by many in the profession to be the most important of the physical factors. Climate can be conducive, passive, or restrictive to many of man's activities. In some areas the governing element of climate may be temperature, in others it may be precipitation, in still others it may be wind or some other climatic element or combination of elements. There are many combinations of temperature and precipitation in the West. This variety results from its wide latitudinal range, its great longitudinal breadth, its high and continuous mountain ranges, its low river valleys, its extensive plateaus, its position downwind from the adjacent ocean, and the characteristics and frequency of the air masses that traverse the region or meet within it. Although the absolute highest and lowest temperatures recorded in this country have been observed within the western states, temperatures, by and large, are satisfactory for raising most of the major food crops. Other climatic elements, except one, are in the main conducive or passive. The restrictive element is water, despite the fact the the largest amount of precipitation in the United States falls in the state of Washington. Except for a few favored areas, most of the West lacks sufficient water at the right time of the year for agriculture unaided by irrigation. In this respect the West is in marked contrast to all the country east of the meridian of 100° west longitude. Agriculturally the West is thirsty. For other activities of man the West is dry, too. Such development as the West has experienced has been largely dependent on water ; and future development will be more and more dependent on water. It has been envisaged by some that the West will finally cease to grow in population, not because of land and opportunities, but because there will not be enough water to support any more people. Mr. John Haw, in an address before the Annual Meeting of the Western Snow Conference in Portland, Oregon, April 22, 1947, said that "every drop that falls, regardless of form, must be held, hoarded, and harnessed to many jobs before it is allowed to escape to the sea." Over the larger part of the West, most of the precipitation comes in the colder half-year; and much of that winter precipitation falls in the form of snow in the high mountains, where temperatures are below freezing . The fact that it falls in the wrong season for agriculture is compensât« ed by its falling in the solid form. It cannot be utilized until it is liquefied. Liquefaction occurs at the right season, agriculturally. Over flat terrain it is easy to obtain a sampling of the amount of precipitation that falls in a year, multiply it by the area and so obtain a first approximation of the total volume of water that falls and will become * Presidential Address before the Association of Pacific Coast Geographers, San Diego, California, June 20, 1947. 1947of Pacific Coast Geographers9 available. In mountains the problem is not so simple. However, where snow falls in the mountains and forms a large fraction of the precipitation for the year, it is possible to forecast quite accurately the amount of water that will flow in the streams during the summer season. Knowledge of the summer water supply in streams is the direct result of snow measurements. These are made approximately on April first, at numerous snow courses in all the Western states. An inventory is thus taken of the water stored in the snow-pack at the end of winter. Most of this water will enter the streams. Because spring and summer precipitation is small, though locally it may form a large percentage of the total annual precipitation, the total stream flow in summer is usually modified only slightly by warm season precipitation. This paper is not the place for a discussion of the methods of determining the water content of the snow-pack or of...