AG 2004 04 19 - Laserfiche WebLink

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~ Water & Sewer Authority of Cabarrus County V~o~,CC Water and Wastewater System Master Plan Safe Yield Update and Regional Drought Operations 2.0 Regional Drought Operations The occurrence of the recent, exceptional drought and the resulting record low levels in the water supply lakes provides great incentive to examine the benefits of managing and operating the water supplies of Cabarrus County in a coordinated manner. The objective of the evaluation of coordinated regional operations is to determine a sequence of operations that best extends the availability of the region's water supply storage in times of drought. A number of local, state, and river-based drought programs were investigated to provide information on similar programs implemented by others. Summaries of these programs are included in Appendix A. 2.1 Staged Water Use Restrictions Water use restrictions are an integral component of any drought contingency plan, and these restrictions should become progressively more stringent as drought conditions increase in severity. Determining the onset and severity of drought conditions requires specific criterion that "trigger" the implementation of ,the appropriate drought mitigation techniques. These indicators must provide sufficient warning for adequate drought response, but not trigger these activities so prematurely or frequently that the public becomes complacent and non-responsive. A four-staged approach to water use restrictions is preferred by WSACC and the member governments, for development of the operational plan. Voluntary Restrictions would occur in Stagg 1; Mandatory Restrictions in Stages 2 and 3; and Emergency Restrictions in Stage 4. The mass-balance safe yield models developed for the four water supply reservoirs (Lake Howell, Kannapolis Lake, Lake Fisher, Lake Concord) provide the basis for developing the drought operating approach. The mass-balance model simulates hypothetical reservoir operations, including interactions with the other reservoirs in the system, using regional hydrologic information to develop a historical reservoir stage record. A number of climatic indicators are available for monitoring drought conditions and triggering stages of drought response. Possible indicators include precipitation, stream flow, groundwater levels, and reservoir storage levels. A discussion of the most meaningful indicators of the water supplies of Cabarms County follows. 2.2 Indicators of Drought Drought indicators are used to identify the onset of deteriorating water supply conditions and provide a warning for appropriate stages of drought response. Initial triggers prompt PN 096873,0800 Janua~ 23,2004 12 BLACK & VEATCH International Company