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<br />. <br /> <br />. <br /> <br />. <br /> <br />W <br />l-" <br />tv <br />l-" <br /> <br />Therefore, the approved standards permit temporary increases above the <br /> <br />1972 levels if control measures are included in the plan. Should water <br /> <br />development projects be completed before control measures are brought on-line, <br /> <br />temporary increases above the criteria could result and these increases will <br /> <br />be deemed in conformance with the standards. <br /> <br />Increases above the criteria as a result of unfavorable reservoir <br /> <br />conditions or periods of below normal annual river flows will also be in <br /> <br />conformance with the standards provided that, with satisfactory reservoir <br /> <br />conditions and when river flows return to normal, concentrations can be <br /> <br />expected to be at or below the criteria level. <br /> <br /> <br />Salt routing studies for salinity projections were made for the 1975 and <br /> <br /> <br />1978 Forum reports using a model developed by the U.S. Bureau of Reclamation <br /> <br /> <br />(Bureau). This model was also used for projecting future salinity con- <br /> <br />centrations for this standards review using current information as regards <br /> <br />future development. For this review, modifications were made to the proce- <br />dures used in estimating the amount of salt entering the river system under <br />1979 (base level) conditions of development. These changes were the result <br />of an analysis of salt tonnages associated with inflow to Lake Powell, <br /> <br />ungaged inflow from Lees Ferry to Grand Canyon, gains and losses in Lake <br /> <br />Powell and bank storage in Lake Powell. Using the results of these studies, <br /> <br />the revised salt load estimate for a virgin flow at Lee Ferry of 14 million <br /> <br />acre-feet per year and 1979 conditions is 741,000 tons less than using pro- <br /> <br />cedures used for the 1978 review. The Forum believes that the new model <br /> <br />inputs more accurately reflect present conditions. <br />Salinity concentrations at each at the three lower main stem stations for <br />which numeric criteria have been established have generally been decreasing <br /> <br />since 1972. Currently, salinity concentrations at the three stations are: <br /> <br />v <br /> <br />. :;1 <br />.IL., , ...... <br />