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,- -- - - -- ... -- .. -- ... -- -- -- -- - -- .- -- Table ES-I, Summary of Potential Impacts of the Execution of the lA, Adoption of the lOP, and Implementation of Biological ?: o :;l " ~ ... ;>0 " ;;- ..- ... ~ ... " , !:. ;.. " - o. :1 .. "" .... '" Conservation Measures (Page 2 of 29) REsource/Issue No Action Impacts of Proposed Action/Alternatives HYDROLOGy/WATER QUALlTY/W A TER SUPPLY Potential impacts to water aualitv from transfers Under No Action, salinity concentralions below Under the lA, projected salinity is similar to that of authorized by the IA. Hoover, Parker, and Imperial Dams are projected to No Action. Below Hoover Dam and Parker Dam, reach objectives by the year 2006. proJected salinity under the IA is no more than 1 Salinity control projects will ensure these objective mg/L higher than would be expected under No Action. At Imperial Dam, salinity is no more than 8 levels are not exceeded. mg/L higher than would occur under No Aclion. However, these impacts will be fully mitigated by implementation of authorized salinity control projects, which will ensure that objective levels are not exceeded. POlential impacls to groundwater from transfers In the valleys below Parker, it is estimated that for The decline in median river stage could result in ~D authorized by the IA. every 1 unit in drop in river elevation, groundwater similar declines in median grou-ndw<tter levels (as under irrigated fields will drop by half a unit. In a much as 4.4 inches)"relativeto the No-Action non-irrigated reach, groundwater elevation drop is Alte~native. Reduction in groundwater elevation assumed to be equal to the river drop. would be greatest in non. irrigated areas and less severe in irrigated areas. Implementation Agreement/Inadvertent Overrun Policy Potential impacts to Colorado River lIood None. Proposed lOP: Under the worst case scenario, releases from inadvertent overruns and payback excess..1lows to Mexico could be reduced by policy. approximately~. On average, excess flows to Mexico could be reduced by approximately 24 KAF. For both the maximum and average overrun account balances, probability of a flood release was decreased by 1 to 3.5 percent in some of the years modeled. No Forgiveness Alternative: Same as the proposed >< project. " " ~ - / o "" .... '" I - " ~ ~ " '-'! '" '" '" '" ~ :,.I(~ ~ "" tT1 '{' .... .... ~ ". " ~ 3 :I " '-'!