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Show PART II NATURE, USE AND MANAGEMENT OF WATERSHED LAND Watershed Characteristics Climate Variations in the region's climate are significant in watershed management. The types and intensity of problems vary with climatic conditions. Likewise there are differences in types of measures needed to solve the problems. Wide variations in precipitation, temperature, and wind movement result primarily from varied topography and to a lesser extent from the rather wide range in latitude. The climate is generally associated with Pacific Ocean air masses which are the source for most of the region's precipitation. During the winter months, Canadian Arctic air occasionally extends into the region. The summer storms sweep into the region from the Gulf of Mexico. Average annual precipitation varies from less than 6 inches at the lower elevations to more than 50 inches in the higher mountains. For most of the region precipitation is heaviest during the winter and spring months. Temperatures vary widely because of seasonal and diurnal effects and differences in elevation. At most climatological stations mean monthly temperatures are lowest in January and highest in July and generally show about a 50°F. seasonal difference. Average annual temper- atures vary from below freezing at elevations above 10,000 feet to about 50°F. for river valleys below 5,000 feet. Vegetal Cover Vegetal cover is significant to the planner in that it is an indicator of the suitability of the land to support various uses. It should be understood that vegetal cover is distinct from land use. For example, commercial timber production is a use of some forest lands, but certainly not of all. Grazing of cattle is a land use on both range and forested lands. |