WSP02775 - Laserfiche WebLink

Home Browse Search

1- , 16 Additional depletions to occupied Colorado squawfish habitats associated with the Project will further reduce monthly average flows at Bluff from 5 percent in a wet year to as much as 70 percent in a dry year (Table 4). Depletions caused by the Project will result in some alteration of physical habitats in occupied reaches of the San Juan River from near Fruitland, New Mexico, downstream 177 river miles to Lake Powell. The specific habitat impacts on this reach of the San Juan River are unquantified at this time; however, depletions caused by the Project (154,800 acre-feet annually) would be compounded by those associated with the operation of the Navajo Dam, San Juan-Chama Project, Navajo Indian Irrigation Project, and other existing uses. Adverse changes in water quality and contamination of associated biota are known to occur in similar Reclamation projects in the San Juan River drainage (i.e., irrigated lands on the Los Pinos and Mancos Rivers) where return flows from irrigation make up a portion of the river flow or other downstream aquatic sites (Sylvester et al. 1988). Increased loading of the San Juan River and its tributaries with soil salts, elemental contaminants, and pesticides from irrigation return flows degrade water quality. In a cooperative Department of the Interior evaluation of irrigation drainage for the San Juan County, New Mexico, water quality data for the San Juan River area indicated the presence of 2-4-0 and diazinon in the water in the San Juan River at Shiprock, New Mexico. The Department study concluded that further investigations into point sources of the contamination and a more thorough coverage of the San Juan River drainage appears necessary. Recent water and tissue sample data are currently being compiled and analyzed. Residual values of chromium copper, lead, and selenium were all above national averages. Selenium concentrations in fish tissue were high enough to suggest the reproductive impairment might already be occurring, The Department study concluded that further investigations into point sources of contamination and a more thorough coverage of the San Juan River 8asin appears necessary (Department of Interior Intensive Desk Evaluation of Irrigation Drainage 1989). The extent of the problem is not known, but research studies planned for the San Juan River Basin will address water quality issues associated with the endangered fish. Colorado Sauawfish Activity: San Juan River In 1986, Reclamation initiated investigations of the San Juan River in response to recommendations in the original 1979 biological opinion (Items 1-4, page 2). An ichthyofauna investigation of the San Juan River in New Mexico and Utah began during the spring of 1987 and finished in 1989 (Platania 1990), producing the following salient biological findings: 1. Colorado squawfish were captured in the San Juan River at several locations between Shiprock, New Mexico, and the inflow area of lake Powell in Utah. No squawfish were captured upstream of the Hogback Diversion Dam located at RM 177 near Fruitland, New Mexico. 2. Successful reproduction of Colorado squawfish in the San Juan River was documented in 1987 and 1988 through the capture of young-of-year specimens (Table 2).