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Q. PRECIPITATION REGIME (1947) <br />The historic record study area is located within the North Fork Valley, an incised <br />riverine drainage valley trending east-west. Two basic types of climate are <br />characteristic of the area of the West Elk Mine (which includes the Historic Record <br />Study Area); semi-arid and undifferentiated highlands (MCC, 1997). The climate of <br />the mine and surrounding area is characterized by a wide temperature Fluctuation; from <br />below freezing in winter, to very warm in the summer months. Precipitation in the <br />area is predominantly provided by Pacific Ocean weather systems and is most frequent <br />and reliable during the winter months. <br />The National Weather Service (NWS) has collected precipitation data in the vicinity of <br />the mine since 1905. The most complete record of precipitation is from the Paonia l <br />SW station located in Paonia, Colorado. This station has been in operation since 1905, <br />and has collected climatic information for 65 individual years at this same location. <br />Table 1 presents a summary of precipitation data collected from the Paonia 1 SW <br />station from 1905 through 1995. A review of the data illustrates that precipitation is <br />lowest during the summer months (June through August) and higher from the autumn <br />through late spring. The months with the highest average precipitation aze October and <br />March. As is illustrated by the maximum and minimum values (as well as the reported <br />standazd deviations), precipitation on a monthly basis can be highly variable. Our <br />calculations yielded an average mean precipitation total of 11.47 inches for the months <br />October through May, from 65 years of record at the Paonia 1 SW station. Based on <br />precipitation records from all locations of the Paonia f SW station from 1905 through -. <br />1995, CDMG calculated a total "pre-growing season" precipitation total of 11.08 <br />inches. This CDMG value was accepted as the mean value for "pre-growing season" <br />precipitation. From this average, comparisons of individual yearly precipitation <br />affecting specific growing seasons can be made. <br />Table 2 illustrates the precipitation prior to the 1997 growing season for the Paonia l <br />SW station. Total "pre-growing season" precipitation was 11.15 inches. This <br />translates into a 0.6 percent positive departure from the CDMG calculated mean <br />precipitation amount (11.08 inches), and as such, represents a "normal" growing season <br />relative to collection of historic record vegetation data in 1997. <br />-2- <br />