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1 <br />Reservoir Drawdown Frequency and Sample Trigger Levels <br />Number of times (or percent of years) during the 77-year streamflow record in which reservoir <br />storage would have declined to 20% or less during the following 18 months. <br />Water Remaining in University Lake and Cane Creek Reservoirs <br />X 100% 95% 90% 85% 80% 75°lro 70% 65% 60% 55% 50°l0 45% 40% 35°h 30% 25% <br />IAG 3358 3190 3022 2854 2686 2519 2351 2183 2015 1847 1679 1511 1343 1175 1007 839 <br />.~._ <br />2002 Reservoir Levels = Highlighted Gells <br />Each cell of the table contains an integer and a percentage, which represent the probability that reservoir levels <br />will decline to 20 percent or Less of full capacity during the following 18 months. These were calculated from <br />spreadsheet model runs of 77+ years of daily streamflow data, updated through January 2003, and driven by <br />initial reservoir storage volume at the beginning of any given month and water demand. These calculations <br />assumed an average annual raw water demand of 9.15 mgd (adjusted by observed monthly ratios}, which <br />was OWASA's average day demand during CY 2001 (i.e., before the drought), and after adjustment for the 10 <br />percent process water recycle. <br />Each row of the table corresponds to a month, and each column corresponds to a reservoir storage level at the <br />beginning of that month. Storage is subdivided into increments of 5% and is also expressed as million gallons <br />(MG). <br />Colors indicate the corresponding conservation and risk levels proposed for each condition. One cell in each row <br />is highlighted in black, representing actual reservoir storage conditions at the beginning of that month during <br />2002. <br />NORM ADV #1 #2 #3 EMRG <br />Conservation Stages and _ <br />_ o-,x a-sx s-r~% <br />Risk Levels <br />