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~ Water & Sewer Authority of Cabarrus County <br />V~CC Water and Wastewater System Master Plan <br /> <br />Safe Yield Update and Regional Drought Operations <br /> <br />I <br />i <br /> <br />to occur in a 10-year period is expressed. For example, based on the previous criteria, <br />Lake Howell is considered to be in a "normal" condition in 57.8 percent of the record. <br />Expressed differently, this is 69 months in a 10-year period. Stage 1 drought conditions <br />occur 38.0 percent of the simulated time. This is equivalent to 46 months in a 10-year <br />period. Drought events resulting in Drought Stage 2, 3, or 4 conditions occur only 4.2 <br />percent of the simulated time, or for a total of 5 months in a 10-year period. <br /> <br /> Table 9 <br /> Duration of Time in Drought Stage <br /> <br />Drought Stage Frequency (%) .! Months in 10-years <br /> Normal 57.8 69 <br /> Stage I 38.0 46 <br /> Stage 2 1.7 2 <br /> Stage 3 0.6 1 <br /> Sta~e 4 1.9 2 <br /> <br />During periods of severe extended drought, conservation measures alone may not be <br />adequate to provide reliable water supply to the communities. Additional water supplies <br />may need to be imported to achieve the desired level of supply reliability. <br /> <br /> } <br /> <br />2.5 Summary <br />The proposed drought curves use Lake Howell reservoir .stage as the primary drought <br />indicator. The analysis of safe yield shows that Lake Howell is limited in its ability to <br />recharge, once its volume and elevation have dropped. Therefore, preserving the volume <br />of water in Lake Howell becomes a priority, once Stage 1 restrictions are implemented. <br />Water use restrictions in concert with reductions in reservoir release are recommended to <br />ensure reliability of the wa~er supply during drought. <br /> <br />PN 096873.0800 22 <br />January 23, 2004 BLACK & VEATCH <br /> ~__________.~.+ International Company <br /> <br /> <br />