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504 Table 2. Summary of stream flows measured during 2001 Summer Low Flow Test. 505 506 507 508 509 510 511 512 513 514 515 Location San Juan River at Archuleta San Juan River at Soaring Eagle Lodge San Juan River above Turley Inlet Channel San Juan River below Hammond Diversion San Juan River below Blanco Bridge San Juan River above Bloomfield Bridge San Juan River below Bloomfield Sewer effluent San Juan River below Lee Acre's Bridge San Juan River 1/4 mile above Animas River River Mile 218.5 216.4 214.4 209.1 207.0 195.8 194.8 188.5 181.4 Flow Average (efs) 267.9 132.7 \31.4 63.0 87.7 130.0 131.1 185.7 218.7 5 I 6 There are four U .S.O.S. gages located in the critical habitat reaches of the river from Fannington 517 to Lake Powell. 518 Water quality standards for the San Juan River are based on water uses. For example, some river 519 segments may be considered of a quality to classifY them as cold water fisheries, while others 520 would be classified as suitable for irrigation or other uses. The river segment from Navajo Dam 52\ to the Blanco Bridge is classified by the State of New Mexico as a "high quality cold water 522 fishery," From there to the confluence with the Animas River, it is considered a "marginal cold 523 water fishery," with different physical standards than the segment upstream. 524 The San Juan River immediately downstream from Navajo Dam is characterized by high quality. 525 Water quality begins to change further downstream due to irrigation return flows, water 526 depletion, erosion of banks, heavy sediment inflow, and other factors. The State of New Mexico 527 has listed parts of the San Juan River that do not meet the intended uses of the river. Turbidity, 528 fecal coliform, and sediment impact the designated uses of the river most often. Some trace 529 elements (selenium, aluminum, arsenic, copper, mercury, and zinc) have exceeded State 530 standards. The table in Attachment C summarizes water quality data collected at project area 531 river gage locations. 532 Studies under the SJRBRIP have identified contaminants of concern to be arsenic, copper, 533 selenium, zinc, and polycyclic aromatic hydrocarbons (PAWs) (Simpson and Lusk, 1999). 534 These studies pointed out potential water quality problems that could affect the endangered fish, 535 and also concluded that concentrations of contaminants in biota inhabiting the mainstem of the 536 San Juan River were not consistently correlated with river flows. These studies did not include 537 extensive sampling of backwater habitats which are important habitats fo~ the endangered fish. 538 The Service (2000) discusses San Juan River water quality concems in more detail. 539 The increased spring releases under the proposed plan would lower concentrations of pollutants 540 because of dilution, while the lower releases during other periods would increase concentrations. 18 (~\v101-