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Show SELECTED WATER- REIATED The Uinta Hydrologic Area is comprised of Daggett, Duchesne, and Uintah counties; large but almost uninhabited portions of Carbon, Summit, and Wasatch counties; and smaller portions of Emery, Grand, and Utah counties. The area is defined as that part of northeastern Utah which is drained by the Green River and its tributaries north of the confluence of the Price and Green Rivers. The boundaries as shown on map # 1 are the Wyoming stateline on the north, the Colorado stateline on the east, the Wasatch Mountains on the west, and the Roan or Brown Cliffs on the south. Climate Perhaps the two most important meteorological elements which characterize the climate of a region are temperature and precipitation. Neither is independent of the other since both are dependent upon solar radiation, topography, elevation, latitude and possibly other undefined phenomena. The climate of a region is determined by a complex combination of meteorological elements including temperature, precipitation, humidity, sunshine, cloudiness, and wind. Climate is generally classed as arid, semiarid, subhumid, humid or wet, depending upon the effectiveness of the precipitation. A measure of this effectiveness has been proposed by Thornthwaite on the basis of an index computed from the following relationship: i= 12 P. E. Index = 115 ^ Pj 10/ 9 i= l Ti- 10 where P^ = mean monthly precipitation in inches, and Ti = mean monthly temperatures in degrees Fahrenheit. Because a precise determination of S OF THE UINTA HYDROLOGIC AREA climatic classification has little practical value, mean annual values of precipitation and temperature were used to compute the P. E. index. The climate was classified on the basis listed in the table below, which is a relationship between the P. E0 index and humidity provinces and/ or type of climate. P. E„ Index Humidity Province 0- 16 Arid 16- 32 Semiarid 32- 64 Subhumid 64- 128 Humid over 128 Wet As map # 2 shows, climatic types in the Uinta Hydrologic Area range from arid in the extreme southern portion to wet in the Uinta Mountains. Map # 3 shows normal annual precipitation in inches. Precipitation in this area varies directly with topography. Weather Bureau records from 1931 to 1960 indicate that the average annual precipitation ranges from less than six inches in the Ouray area to more than forty inches in the peak areas of the Uinta Mountains. It should be noted that precipitation in a specific year may vary considerably from the values shown on the map. Precipitation is quite uniform throughout the year, but a greater amount falls in the October- April period than in the May- September period. Most of the winter precipitation falls in the form of snow while summer precipitation is characterized by thunderstorm activity, resulting from the northward flow of warm moist air masses from the Gulf of Mexico. The southeast slope of the Uintas is the principal area of heavy thunderstorm activity in the State of Utah. The frost free season map, map # 4, shows the average number of days per year between the last freeze in the spring and the first freeze in the fall. |