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<br />.' <br /> <br />.~ <br /> <br />,:-i) <br /> <br />."h' ~ ?~.., ;,.",\ -..-.;.,'It,._'''''..:t....,,. ......,~... ~.oe:Joo.~,'p <br /> <br />-._<- ~ '. .... <br /> <br />. <br /> <br />7 <br /> <br />project is 465.649 MAF, divided by 34 yesrs which equals 13.695 MAr; this flow <br /> <br />less Compact and Mexican Treaty deliveries equals 5.446 MAF. !his final number <br /> <br />represents Upper Basin depletions assuming no shortages. If an aversge shortage <br /> <br />of 6.11 percent is assumed (2.1 MAF of M&I uses with no shortage and 3.7 MAF of <br /> <br />irrigation with an average shortage of 10 percent), we divide 5.446 MAr by 93.89 <br /> <br />percent which gives the 5.8 MAr Upper Basin possible depletion. <br /> <br />The effect of sediment accumulation in Lake Powell was also evaluated. <br /> <br />Preliminary Planning studies indicate that the total 100 year volume of accumu- <br /> <br />lated sediment in Lake Powell would be 8.54 MAF, 3.9 MAF of which would be <br /> <br />expected to deposit above the minimum power pool. Consideration of this volume <br /> <br />of sediment in the above equation changes the computed depletion by only 2 per- <br /> <br />cent. <br /> <br />There are two different hydrology data sets avsilable thst were used with the <br /> <br />formula to evaluate and verify the present 5.8 MAF determination. The hydrology <br /> <br />data sets are used with the formula to determine average streamflow and the cri- <br /> <br />tical period. These are discussed below: <br /> <br />1. Virgin Flows - Virgin flows are computed, undepleted flows at Lee Ferry. <br /> <br />They are available on an annual basis for the period 1896 to 1981. <br /> <br />2. Colorado River Simulation System (CRSS) Natural Flows - these are also com- <br /> <br />puted, unregulated, undepleted flows at Lees Ferry. They are computed on a <br /> <br />monthly basis taking into consideration Bureau and non-Bureau reservoirs, trans- <br /> <br />basin diversions and imports, municipal and industrial uses, and depletions from <br /> <br />consumptive use computed by the modified Blaney-Criddle method. While monthly <br /> <br />natural flows have been determined for 19 stations in the Upper Basin for use in <br /> <br />'I <br /> <br />~ <br /> <br />"'1 <br /> <br />, <br />'., <br /> <br />r~ <br />~. <br />L <br />; \ <br />\.: <br /> <br />., <br />J>: <br /> <br />t.<. <br /> <br />if, <br />'~ <br />~{ <br />l,i <br /> <br />2~'-~ I <br />j,;" <br />r'~~ <br />.i'~ I <br />~fi; <br />!.~- . <br />t{ <br />.!l;," <br /> <br />l.-.,j <br />~: <br />t": ' <br /> <br />~} <br />t" <br />~ ", 1 <br />H';', <br />Ht <br />l{.; <br />I"~ <br />f~ <br />! ,.. <br />..."r~ <br />r~ <br />i-.~~ <br />r~ <br />ft? <br />(_ ~.;1 <br />I' .... ~ <br />r.:;' <br />r~ <br />; ,,~~ <br />\,,,- <br />t .? <br />t"- <br />~ - . <br />..F <br />, . <br />t <br />r . <br /> <br />~ <br /> <br />r <br />" <br />~.. <br />~. <br />,. <br />,. <br />f <br />r <br />~ <br />