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- rn '{' - o Table ES-l, Summary of Potential Impacts of the Execution of the lA, Adoption of the lOP, and Implementation of Biological Conservation Measures (Page 1 of 29) '" .. " ~ ~ ~. " ~ ~ 3 " ~ N '" '" N I Rt:source/lssue No Actioa Impacts of Proposed ActioajA/fematives HYDROlOGY!W A TER QUAlITY/W A TER SUPPlY Implementation Agreement Potential impacts to Colorado River flows from Projected A verage Annual Flow (MAFY): Primary impacts are in the reach between Parker transfers authorized by the IA. Glen Canyon to Hoover Dam: B.23 to 10 Dam and Imperial Dam. Below Parker Dam, due 10 Hoover Dam to Parker Dam: 8.54 to 9.72 transfers authorized by the lA, average annual flows Parker Dam to Imperial Dam: would decrease from 138 KAF to 388 KAF. This At Headgate Rock Dam: 6.72 to 6.8 could result in lowering of median annual surface Below Palo Verde Diversion Dam: 6.02 to 6.16 water levels by LIP to 4.4 inches in this reach. Potential impacts to reservoir levels from Lake Powell levels are expected to be lower than Lake Powell and Lake Mead water surface transfers authorized by the IA. historic levels due to increased Upper Basin devations would decline under No Action and this depletions. Median Lake Powell levels are trend would continue with implementation of the expected to decline for a number of years and then IA. The IA would not cause a significant change slabilize. In Ihe shorllerm (years 2002-2010), Lake relative to No Action in the anticipated lake levels. Mead levels would be greater than that needed to ptoduce electricily. However, after year 2011. there would be '" 44% probability that Lake Mead would fall below 1083 feet ms!. Through 2017, modeling results show that Lake Mead levels would exceed that needed for operation of SNW A's original intake (1050 feet msl), after 2017, reservoir levels would decline and there would be a 40% probability that Lake Mead would be lower than 1050 feet mean sea level (msl). During years 2002 through 2049, modeling shows that Lake Mead . levels would be greater than n(..~essary to operate Southern Nevada Water Authority's (SNW A) second waler intake (1000 feet msl). But after 2049 there would be a 6% probability thaI Lake Mead elevation would be below elevation 1000 feet msl. / t.!P . C,. v o '" - <r> I - " ~ " ~ ?= i3 :c " " "- ~ " D - " "- ." " "- " ~ " :.. " :to o " '" '" - <r> '. :- J_ - -- - - - - - .. - - ,. ,- :-.-