1999-04-26_PERMIT FILE - M1999051 (2)

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EXHIBIT K CLIMATE Colorado exhibits two distinct climatic regions. The eastern half of the state is high plains, consisting of flat, even terrain which slopes gently to the east. The high plains are described in climatic terms as "continental" because they are well removed from most direct influences of oceans or large bodies of water. The high plains are generally dry, receiving only 12 to 14 inches of precipitation each year. This moisture is usually in the form of locally heavy thunderstorms during the summer and heavy snows during the winter when moisture laden systems flow from the midwest and Gulf states. The western half of Colorado exhibits a much greater variability in climate due to the extreme variations in elevation and to local topographic features. Normal precipitation in the area ranges from 7 inches to greater than 25 inches annually. Much of the annual precipitation in western Colorado occurs during the winter months when storm systems from the Pacific Northwest bring moisture and cold temperatures to the mountains. Moisture is removed as the systems pass over the higher elevations. Some locally heavy thunderstorms occur in the summer, resulting in occasional localized debris and mud flows. The Rock School project area is in the Piceance Creek Basin of northwestern Colorado. The Basin's climate is classified as semiarid continental. However, the areas of higher elevation, with their attendant higher precipitation and lower evaporative demands, could be classified as sub-humid. This region also lies in the path of several major storm tracks. Storm systems originating in the Gulf of Mexico, in the Pacific coastal region, and in the Gulf of Alaska all have the potential for delivering moisture to western Colorado. However, several major mountain systems lie between the Piceanse Basin and the storm sources. These mountains act as barriers to reduce the amount of moisture available for precipitation. Annual precipitation averages 17.4 inches, and ranges from 12 inches in the valley bottoms to more than 25 inches on the top of the plateaus. Selected sites on the plateau may receive in excess of 30 inches of effective precipitation annually because of snow redistribution by wind. Precipitation is very evenly distributed over the year with month-to- month variations generally less than one inch for the long-term norm. Rainfall intensities are generally light, although intensities exceeding two inches per hour for durations less than 30 minutes occasionally occur at the lower elevations. Snowfall accounts for about 40 percent of the total precipitation, with the remainder falling during the summer when intense, short- term thunderstorms frequent the area. G:\LMW\78545.002\Reclamation\Reclamexh.DOC K-1