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<br />Data Sources <br /> <br />- <br />27 <br /> <br /> <br />the period of regulation on the American. <br />Order-of-magnitude estimates of potential error related to stage <br />measurement also point to other factors responsible for increased flood magnitudes in <br />the more recent period. At capacity, Folsom Reservoir contains approximately <br />1,000,000 acre-feet of storage and covers approximately 12,000 acres (NRC, 1995). <br />It is assumed that daily changes in storage (tlSf,t) are obtained directly from stage <br />measurements applied to a rating curve. For a hypothetical stage measurement error <br />of 1.0 foot at maximum stage (storage), or approximately 0.4% relative to the 260-ft <br />maximum depth of pool, the corresponding error in storage is 12,000 acre-feet, or <br />6,050 cfs-days. In comparing this number to the 1986 peak one- and three-day <br />maxima of 171,000 and 166,000 cfs (daily mean), the resulting relative errors are <br />3.54% and L2l %, respectively. For any stage below that design capacity, the <br />corresponding percentages would be lower. These are presumably within the range <br />of gaging error, particularly when gage measurements represent extrapolations of the <br />rating curve well beyond any discharges measured by current meter, as would be the <br />case for an extreme flood. <br /> <br />Cumulative Folsom Inflow <br /> <br /> <br /> <br /> <br />FOLSOM DAM CONSTRUCTED <br /> <br />., 00000o <br />o <br /> <br />200000 <br /> <br />"""'" <br /> <br />600000 <br /> <br />600000 <br /> <br />, 00000o <br /> <br />, 200000 <br /> <br />Cumulative North For1<. Dam Inflow <br /> <br />FIGURE 2.5 Cumulative peak annual inflows to North Fork Dam (North Fork of the <br />American River) vs. cumulative peak annual inflow to Folsom Dam (1942-1996). <br />