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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 />For each lake, the month and year that resulted in the lowest lake elevation is also <br />identified. The results are shown in Table 3. <br /> <br /> Table 3 <br /> Significant Water Supply Droughts (1900-2002) <br /> <br />Rank Year Mont~ Safe Yield (mgd) Rank Year Month 'Safe Yield (mgd) <br />1 2002 October 7.05 ~ ' I 2002 September 5.70 <br /> 2 1956 November 16.20el~ 2 1956 November 8.50 <br /> 3 1927 Novem,ber 16.30 ~ 3 1927 November 8.60 <br /> 4 1970 July 18.00 ~ 4 1986 November 8.65 <br /> 5 1942 November 18.30,,~ 5 1981 November 8.95 <br /> 6 1986 December 18.50 ~ 6 1967 November 9.00 <br /> 7 1981 November 18.80~ 7 1942 January 9.00 <br /> 8 1932 Septem.ber 19.05 8 1931 November 9.20 <br /> 9 1914 Novemb, er 20.25 <br /> 10 1994 Decemb, er 21.00 Rank Year Month Safe Yield (ml~d) <br /> 1 2002 October 3.00 <br />Rank Year Month, Safe Yield (m~d) ~ 2 1986 November 5.15 <br />1 2002 October 0.70 ,~ 3 1956 January 6.35 <br />2 1986 November 1.20 '~ 4 1926 October 6.55 <br /> 3 1956 January 1.55~ 5 1981 November 6.65 <br /> 4 1925 Deceml:[er 1.60 ~, 6 1967 November 6.90 <br /> 5 1981 December 1.65 7 1993 December 7.00 <br /> 6 1993 November 1.70 8 1931 November 7.10 <br /> 7 1967 Novemb, er 1.70 9 1983 November 7.35 <br /> 8 1930 November 1.75 <br /> <br />1.5.2 Fifty-Year Safe Yield. The 50-year safe yield is computed for each reservoir to <br />meet the North Carolina Department of Environment, Health, and Natural Resources <br />guidelines. The guidelines base the safe yield of an impounded surface water source <br />serving more than 50,000 people on a 50-year drought. Each of the four reservoirs was <br />evaluated to determine its safe yield, using a 50-year drought recurrence interval. <br /> <br />Since approximately 100 years of reservoir operations are simulated, the most detrimental <br />drought event of the period is determined to have a 100-year recurrence, and the second <br />most significant drought, is determined to have a 50-year recurrence. A .summary and <br />comparison of these safe yield values to previously published values is in Table 4. <br /> <br />PN 096873.0800 8 [;~, <br />January 23, 2004 BLACK & VEATCH <br /> C ~, International Company <br /> <br /> <br />