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<br />22
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<br />Basin. Table 2 identifies each project in the baseline and its associated
<br />depletions,
<br />
<br />Included in the baseline, along with a number of other smaller water projects,
<br />are existing operational portions of the Navajo Indian' Irrigation Project,
<br />which was authorized on June 13, 1962, to provide irrigation water for
<br />110,630 acres of Navajo-owned land in northwest New Mexico, generally south of
<br />Farmington, Construction of the Navajo Indian Irrigation Project began in
<br />1973, and limited operation began in 1976 and 1977, The Navajo Indian
<br />Irrigation Project is being constructed in blocks of 8,000 to 10,000 acres,
<br />based on congressional appropriations, Through 1990, 6 blocks were completed
<br />with a total of 54,500 acres developed, representing an annual depletion of
<br />132,980 acre-feet. On January 12, 1995, the Service issued a biological
<br />opinion for Blocks 1 through 8, therefore, the updated baseline shows Blocks 7
<br />and 8, with water required for the additional blocks taken from existing
<br />Navajo depletions within the baseline, The Hogback and Fruitland Projects
<br />were limited to an aggregate depletion of 31,280 acre-feet with the remaining
<br />16,420 acre-feet transferred to the Navajo Indian Irrigation Project, Thus, no
<br />further depletions were associated with Blocks 7 and 8, Existing depletions
<br />caused by the San Juan-Chama Project and evaporation losses from the Navajo
<br />Reservoir also are included in the baseline,
<br />
<br />The analysis quantified the post-Project condition by adding the full
<br />Animas-La Plata depletions of 149,220 acre-feet to the baseline of
<br />570,500 acre-feet (a depletion of 592,500 acre-feet upstream of the Mancos
<br />River, with a return flow of 22,000 acre-feet from the Dolores Project)
<br />identified in Table 2, This results in a post-Project depletion in the San
<br />Juan River Basin of 719,720 acre-feet, or 38 percent of the 1,9 MAF mean
<br />annual yield.4 '
<br />
<br />The depletion numbers used in the analysis were provided by Reclamation for
<br />the wet, average, and dry years described above, The changes in river flow,
<br />based upon this full development, were quantified for the Project effects
<br />analysis. These changes were analyzed and a summary of the changes between
<br />baseline and post-Project flows is presented in Table 3,
<br />
<br />4
<br />
<br />A mean annual yield of 1,9 MAF for the San Juan River Basin has
<br />been used throughout this report and is consistent with the period
<br />of record used in the hydrological analysis, Reclamation has
<br />estimated that the long-term mean annual yield of the San Juan
<br />River Basin is 2,2 MAF, The period 1929 - 1974 was the data
<br />available in the San Juan River operations model and reflects the
<br />lower basin yield.
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