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The following sections describe the comparison of combined gage locations and provide details <br />related to combining the gage data. <br />Clear Creek <br />In 1979, the Clear Creek near Golden (06719500) gage was discontinued. The Clear Creek at <br />Golden (06719505) gage, which is located approximately 0.7 miles downstream of the original <br />gage, provides date starting in 1974. The Clear Creek near Golden gage data were utilized from <br />1950 through 1974, and the Clear Creek at Golden gage data were used for the remainder of the <br />study period. <br />Together, the two Golden gages provide historical data for the entire SPDSS study period. <br />However, the Church Ditch is located between the old and new Golden gage locations. To <br />combine the Golden gages, historical diversion data for the Church Ditch (0700540) were <br />subtracted from the Clear Creek near Golden historical gage data for the period 1950 through <br />1974, effectively adjusting the Clear Creek at Golden gage data downstream to the current <br />location. <br />North Fork South Platte River <br />In1998, the North Fork South Platte River below Geneva Creek Canyon at Grant (06706000) <br />gage was discontinued. The North Fork South Platte River at Grant (PLAGRACO) gage, which <br />is located 0.1 miles upstream of the original gage, provides data starting in 1990. The below <br />Geneva Creek Canyon at Grant gage data were utilized from 1950 through 1989, and the at <br />Grant gage data were used for the remainder of the study period. <br />Together, the two Grant gages provide historical data for the entire SPDSS study period. There <br />are no major diversions or tributary inflows between the old and new Grant gage location and <br />there is less than a 1% difference in contributing drainage area to each gage location, according <br />the USGS. <br />The Harold D. Roberts Tunnel diversion is located upstream of both the old and new gage <br />locations. The Roberts Tunnel began diverting in 1964, long before the stream gage was moved. <br />This is evident from the break in slope in 1964 in the cumulative flow diagram shown in Figure <br />5. However, there is no break in the slope for the combined North Fork South Platte River gages <br />in 1998, when the gages were combined, indicating that there are no major streamflow <br />differences between the two gage locations. Therefore, the two gages were combined without <br />any further adjustment. Roberts Tunnel diversions will be accounted for in the base flow <br />analysis of the potential future surface water modeling. <br />Task2.doc 17 of 30 <br />