Laserfiche WebLink
<br />The San Juan River is characterized by good water quality immediately below Navajo Dam. <br />Downstream the quality begins to degrade due to irrigation return flows, water depletion, erosion <br />of banks, heavy sediment inflow, and other factors. The State of New Mexico has listed parts of <br />the San Juan River that do not meet the intended uses of the river. Turbidity, fecal coliform, and <br />sediment impact the designated uses of the river most often. Some trace elements (selenium, <br />aluminum, arsenic, copper, and zinc) have exceeded State standards. The tablc in Attachment C <br />summarizes water quality data collected at project area river gage locations. <br /> <br />Under the No Action alternative, it is assumed that Navajo Dam and Reservoir would be <br />operated as it was from 1973 to 1991, with a minimum release of 500 cfs. Operational goals <br />include to store as much water in the reservoir as possible and maintain uniform flows <br />downstream. The No Action alternative does not mimic the natural hydrograph and it is assumed <br />that projects that rely on such mimicry for ESA compliance (for example, Animas-LaPlata and <br />completion of NIlP) would not be included in the baseline depletions. <br /> <br />SPECIES ACCOUNTS <br /> <br />The following sections address the effects of the proposed action on threatened and endangered <br />species, candidate species, and other species of special status. Table 2 summarizes the findings <br />of this assessment. Information is provided on species distribution and habitat needs and <br />impacts of the proposed operation changes are presented. For some species, there is an <br />abundance ofliterature on habitat requirements and other factors; this assessment summarizes <br />appropriate information and the reader should refer to technical reports and papers for detailed <br />information. <br /> <br />Endangered Species <br /> <br />Colorado Dikeminnow <br /> <br />The Colorado pikeminnow is endemic to the Colorado River system and occurs in low numbers <br />in the Green River and the Colorado River upstream from Lake Powell and in their major <br />tributaries. The species does not reproduce in reservoirs and construction of Glen Canyon Dam <br />and Navajo Dam has isolated the San Juan River population from other Upper Colorado River <br />populations since the 1960's. <br /> <br />According to reports reviewed in Holden (1999), there is little information on historical <br />abundance in the San Juan River although anecdotal information suggests the pikeminnow was <br />common and extended upstream into what is now Navajo Reservoir. Based on SJRBRIP <br />surveys, there are likely fewer than 100 adult pikeminnows and maybe fewer than 50 at the <br />present time (Holden, 1999). <br /> <br />Critical habitat has been designated for the pikeminnow along the lower San Juan River as <br />follows: <br /> <br />15 <br />