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<br />w <br />UI <br />CJt <br />o <br /> <br />" <br /> <br />5. Implementation of the salinity portion of <br />individual State Section 208 Water Quality Management <br />plans, as approved by EPA. . <br />Although th~ plan of implementation is designed to <br />maintain thp numeric criteria under an assumed long term <br />water supply, many natural and marimade fsctors affect the <br />river's salinit~.. Consequently, sslinity will var~' from <br />year' to year and may temporarily exceed the adopted numeric <br />criteria in some years and fall below\the criteria in <br />others. <br />The salinity control plan is designed to keep any <br />temporary increases above the numeric criteria to a minimum <br />as well as reduce the duration of :suchtemporary <br />increases. Any increases in salinity above the criteria <br />rJ'sul tin. from human acti vi ties are expected to be small <br />and of short duration. However. should water development <br />projects be completed before contrril measures are brought <br />on ]Jnp, t.emporar~' increases above. the criteria could <br />rpSll I t and thesp i nc'reasE'swi 1 I bp' deemed in conformance <br />with the standards If approprlat.e salinity control meaSUrE'S <br />are IncluriE'ri in the plan. <br />Increases abovE' the criteria. as a reault of <br />unfavorable periods of below normal annual river flows and <br />resulting unfavorablE' reservoir conditions will also be <br />considered in conformancE' with the standards, provided that <br />when :rlvE'r f101's return to normlll and !;atisfacton' <br />resp~voir conditions ~~E'vall,6oncentrations can ~e. <br />exppcted t.o bp at or below the criteria level. <br />Salinity concentrations at each of the lower main <br />stpm stations for which numeric crit~ria have been <br />estahllshpd havE' decreased significantly since ]983. Thp <br />pprlod ]9R~-86 has bppn a period of extremely high runoff <br />and exc~ss flows in the lower rivet have caused a large <br />tpmporary reduction in salinity concentrations. Current <br />salinjly concpntrations at thE' three salinity critpria <br />stations are: <br /> <br /> <br />/ <br /> <br />Numeric <br />criteria <br />in mill <br /> <br />]986 salinlt~. <br />concentration <br />in mg Il <br /> <br />Salinity <br />t'onoentration <br />bel 0'" numeric <br />criteria in mg/] <br /> <br />Below'Hoover Dam <br />Below Parker Dam <br />Imperial Dam <br /> <br />723 <br />747 <br />879 <br /> <br />519 <br />559 <br />579, <br /> <br />204 <br />188 <br />300 <br /> <br />,{,V <br />