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<br />Developing Salinity Control Targets <br /> <br />return flows be completed before control measures, temporary increases <br />above the criteria could result, and these will be in conformance with the <br />regulation. With completion of control projects now in the plan or those to <br />be added subsequently, salinity would return to or below the criteria level. <br /> <br />The goal of the Colorado River Basin Salinity Control Program is to <br />maintain the flow-weighted average annual salinity at or below the numeric <br />criteria of the salinity standards. The salinity control program is not, <br />however, intended to counteract the salinity fluctuations that are a result of <br />highly variable flows caused by climatic conditions, precipitation, snowmelt, <br />and other natural factors. Therefore, to evaluate the effectiveness of the <br />salinity control program, water quality data are adjusted using a computer <br />model to normalize the data so that they reflect average hydrologic <br />conditions. <br /> <br />Figure 2 compares the normalized <br />salinity to the numeric <br />criteria at Imperial Dam. <br />This is a computer generated <br />comparison which removes <br />hydrologic variations from <br />the observed salinity. <br />Reclamation first runs a <br />computer model of the river <br />to confirm that the model is <br />accurately re-creating <br />historic salinity levels <br />observed in the river system. <br />Next, the entire range of <br />flows (1906-present) is run <br />for a particular year (or level <br />of water development). This <br />produces a flow-weighted <br />average annual salinity for <br />that particular year. This <br />average is then compared to the <br />numeric criteria of the standards. <br /> <br />1100 <br /> <br />1000 <br /> <br />~ 9DO ___ . _. _..~u~~ccriterla-~,~__. <br />r _ /"'__ _-...... <br />i ~// ---.----......./ ---------/.....---- <br />-800 <br />Jl SaUnlty adjusted to average <br />fla.v conditions for <br />comparison to the numeric <br />criteria of the salinity <br />standatds. <br /> <br />700 <br /> <br />I <br />800 ' <br />1965 <br /> <br />1970 <br /> <br />1975 <br /> <br />1980 <br /> <br />'986 <br /> <br />1990 <br /> <br />Figure 2.-Normalized or "flow-adjusted <br />"salinity at Imperial Dam. <br /> <br />Reclamation updates this evaluation periodically to assess whether current <br />salinity control projects are sufficient to meet the numeric criteria of the <br />salinity standards. Figure 2 su=arizes the results of this analysis over <br />the past 25 years. The figure shows that the numeric criteria of the <br />standards have been consistently met. The salinity control program has <br />offset the effects of future water development in compliance with the <br />standards. <br /> <br />ooe;:; 8 <br /> <br />21 <br />