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<br />, ;i' <br /> <br />38 Chapter 3.0 Affected Environment and Environmental Consequences <br /> <br />3.2 WATER <br />3.2.1 Affected Environment <br /> <br />The indicators used to evaluate impacts on water are dam releases, flood flows, reservoir <br />storage, water allocation, Upper Basin yield, and water quality. The powerplant fluctuations <br />allowed prior to the ROD are now limited in their daily maximum and minimum, and in the rate at <br />which they change from those upper and lower limits. Water released from the dam is now much <br />colder than before Glen Canyon Dam was constructed (averaging 460F) and varies only about 80F <br />year-round. During the summer months and lower flows, the water warms as it flows downstream. <br />The dam releases clear water, and the river becomes muddy only when tributaries contribute <br />sediment. <br /> <br />3.2.2 Environmental Consequences <br /> <br />Annual dam releases as determined by the Secretary's long-range operating criteria and <br />law will be the same under both the No Action and Proposed Action alternatives; however, <br />monthly release volumes would differ depending on when and in what order the four <br />sediment input scenarios are implemented. Table 2.2 shows the monthly release volumes for <br />the No Action Alternative and the various scenarios of the Proposed Action Alternative if <br />they were to occur during water year 2003. (A "water year" runs from October 1 through <br />September 30.) The resulting downstream water surface elevations for the various hydrologic <br />components of the Proposed Action are listed in table 3.2 for five gauging stations locations <br />between Glen Canyon Dam and Lake Mead. <br /> <br />If the Proposed Action were implemented, the fluctuating non-native fish suppression <br />flows would cause January-March releases to be slightly higher and the October-December <br />releases to be slightly lower than under the No Action Alternative. <br />The sediment conservation releases would cause January releases to be higher and the <br />October-November releases to be slightly lower than the No Action Alternative. <br /> <br />Lake Powell is currently (September 2002) about 70 feet from full. This has resulted in <br />annual releases during 2002 and expected annual releases during water year 2003 to be at the <br />minimum objective annual release level of 8.23 maf. A return to greater precipitation in the <br />Colorado River Basin will not likely affect fall releases until Lake Powell approaches full <br />capacity. Should equalization releases be required after water year 2003, they would be <br />scheduled in the summer months and would not have any effect on the experimental flows. <br />