Water Resources Professional Project Reports

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Technical Report

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Similar to many dams around the world, Cochiti Dam [since its construction in 1975 on the Middle Rio Grande (MRG), New Mexico] has contributed both benefits and negative impacts to those who make use of the MRG. Built primarily for flood control, the dam has resulted in significant geomorphic changes below the dam. This has caused the decline of some native organisms adapted to the river. Since 1994, the Rio Grande silvery minnow (RGSM) (Hybognathus amarus) has been federally listed as an endangered species. Habitat availability is a concern for the species, which currently occupies only about 7% of its historical range. Since 2002, the U.S. Fish & Wildlife Service has conducted RGSM experimental augmentation efforts in an attempt to re-establish populations in the MRG for spawning and recruitment. A small-scale habitat availability evaluation for RGSM was conducted at Peña Blanca, located in the Cochiti-Angostura reach of the MRG. Surveys were conducted during fall (November 2006), winter (February 2007), and spring (April 2007) seasons. Macrohabitat characterizations include: transect data of available depths and velocities of a given flow, a hydrograph comparison of three U.S. Geological Survey (USGS) gauges, and an examination of active channel changes within the Cochiti-Angostura reach. An exceedence probability curve was generated using historical gauge data, while a GIS overlay analysis was completed using active channel data from 1992 and 2006. Mesohabitat characterizations included habitat type, substrate type, and fish community surveys. In order to put the Peña Blanca site in context with downstream sites, three previously surveyed (2002-2004) sites by U.S. Fish and Wildlife were chosen (La Orilla, Los Lunas, and Bosque del Apache) to compare and contrast macro- and meso-habitat variables between sites. Despite both seine haul and backpack electrofishing techniques, no RGSM were collected at the Peña Blanca site. The exceedence probability curve generated from the three USGS gauges indicates the Cochiti-Angostura reach experiences generally higher average discharge than the two lower reaches (Isleta and San Acacia), and less hydrographic diversity. Transect velocity profiles also indicate most velocities at Peña Blanca are between 1.5 and 4 ft/sec. Meso-habitat characterization results, specifically habitat type and substrate, suggest minimal areas suitable for RGSM. Findings of this study suggest that the Peña Blanca site has minimal RGSM habitat. Results also confirm that Peña Blanca is significantly different compared to sites in the southern Isleta and San Acacia reaches in terms of velocities, substrate, and habitat type. Habitat for RGSM is minimal at Peña Blanca; however, habitat restoration efforts conducted throughout the Cochiti-Angostura reach could enhance the area in terms of habitat availability. Recommendations include surveying Peña Blanca during summer months, modifying sampling techniques, and communicating with neighboring Pueblos to encourage habitat restoration efforts as a part of their own Fishery Management Plans.

Language (ISO)



Rio Grande silvery minnow (Hybognathus amarus), Cochiti-Angostura river reach, habitat restoration, Fishery Management Plans, Rio Grande Silvery Minnow Recovery Plan


A Professional Project Report submitted in partial fulfillment of the requirements for for the degree of Master of Water Resources, Water Resources Program, University of New Mexico.