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~ Water & Sewer Authority of Cabarrus County <br />~----~ Water and Wastewater System Master Plan <br /> <br />Safe Yield Update and Regional Drought Operations <br /> <br />2.3 Evaluation of Reservoirs during Drought Conditions <br />The purpose of simulating and evaluating the operations of each of the four reservoirs is <br />to determine the preferred manner of managing the raw water sources of Cabarms <br />County during periods of drought. In the analysis, each reservoir is' analyzed <br />independently and as part of the system. Three specific drought periods were considered <br />(1950s, 1980s, and 1998-2002) to evaluate reservoir response to droughts with different <br />characteristics. <br /> <br />Operation of the reservoirs was analyzed over the recent, record drought. Each reservoir <br />was simulated to operate at a flow equal to the safe yield values computed for the <br />drought-of record (Table 4). Remaining volume in each reservoir and total system <br />volume is plotted over time in Figure 12. The figure shows the strong relationship <br />between Lake Howell volume and total remaining volume available to the system <br /> <br />7OOO <br /> <br />6000 <br /> <br />500O <br /> <br />i4000 <br /> <br /> 3000 <br /> <br />2000 <br /> <br />1000 <br /> <br /> 0 <br /> <br />t .... z ~ ' -q :; z z <br /> <br />Figure 12. Reservoir simulation during drought of record, withdrawals at 100-yr safe yield <br /> <br />It is useful to refer back to Figures 7, 8, 9, and 10 to analyze reservoir behavior with <br />withdrawals equal to the 50-year safe yield. Although the recent drought is the drought- <br />of-record for all four reservoirs, the next most severe drought, the basis of the 50-year <br />safe yield, is not the same for all reservoirs. The 50-year safe yield of Lake Howell and <br /> <br />PN 096873.0800 <br />January 23, 2004 <br /> <br />BLACK & VEATCH <br /> International Company <br /> <br /> <br />