Upper Rio Grande - Bravo
Text modified from Abell et al. 2000. Freshwater Ecoregions of North America: A Conservation Assessment. Island Press, Washington, DC, USA. Additional text provided by Jennifer Hales.<
Major Habitat Type
Temperate upland rivers
Drainages flowing into
During the late Tertiary and early Quartenary the Upper Rio Grande ended in the endorheic basins of south-central New Mexico, Trans-Pecos Texas, and northern Chihuahua; later, during the mid-Pleistocene the upper section joined with the Lower Rio Grande to flow into the Gulf of Mexico (Smith & Miller 1986).
Main rivers to other water bodies
Major tributaries to the Upper Rio Grande are the Rio Chama, Rio Puerco and Rio Paraje, and Alamosa rivers. Dams have created the major reservoirs of Elephante Butte, Cochiti, Abiquiu, Angostrura, Isleta, San Acacia and El Vado.
This long narrow ecoregion begins in the middle portion of southern Colorado, extending through west-central New Mexico into western Texas. The watersheds of the Rio Grande, from its headwaters to the mouth of the Río Conchos in Mexico, form this ecoregion’s boundary. The eastern extent of this ecoregion is partially defined by the Sangre de Cristo Mountains, while the western extent is defined by the series of ranges that create the Continental Divide. The Rio Grande flows through New Mexico’s major cities, and over 80% of New Mexico’s human population lives along the river (Forest Guardians 1998). In Mexico this river is known as the Río Bravo del Norte.
The headwaters of the Rio Grand begin in the San Juan Mountains in southern Colorado, and flow through a series of valleys and basins (Smith & Miller 1986).
The Rio Grande’s headwaters are in the San Juan Mountains in southern Colorado, and from there the river flows south through the San Luis Valley and the Rio Grande Depression. The character of the river changes markedly when it exits the depression below El Paso, Texas, and it is this change that signals the break between the Upper and Lower Rio Grande. Streams in the upper portions of this ecoregion tend to have relatively predictable flow regimes and contain fairly diverse habitat types. Further downstream, tributaries are more widely spaced and flow in them is erratic, with the portion of the Rio Grande between El Paso, Texas and the Río Conchos at times virtually dry (Smith & Miller 1986).
Terrestrial habitats in the ecoregion range from coniferous forests to xeric shrublands, sagebrush and grasslands of the Colorado Plateau and Chihuahuan Desert (Ricketts et al. 1999).
Description of endemic fishes
There is only one endemic fish species, the White Sands pupfish (Cyprinodon tularosa), which is the only fish species found in three restricted areas in the endorheic Tularosa Basin (Propst et al. 1985; Miller & Smith 1986). The Rio Grande silvery minnow (Hybognathus amarus) was once found in the Upper and Lower Rio Grande  as well as the Pecos River , but today is restricted to a reach of the Rio Grande between Cochiti Dam and Elephant Butte Reservoir, in central New Mexico.
Other noteworthy fishes
Historically, the Upper Rio Grande also shared with the Lower Rio Grande the phantom shiner (Notropis orca) and the Rio Grande bluntnose shiner (N. simus simus), both of which are now extinct.
Justification for delineation
Ecoregion boundaries are taken from Abell et al. (2000) and are based on subregions defined by Maxwell et al. (1995).
- Forest, G. (1998) \Water and the Rio Grande\
- Miller, R. R. and Smith, M. L. (1986). "Origin and geography of the fishes of central Mexico" C. H. Hocutt and E. O. Wiley (Ed.) The zoogeography of North American freshwater fishes ( pp. 487-517 ) New York, New York, USA: Wiley.
- Propst, D. L., Hatch, M. D. and Hubbard, J. P. (1985) \White Sands pupfish (Cyprinodon tularosa)\ New Mex. Dept. Game and Fish, Handbook Spec. Ed. in New Mexico: FISH/CT/CY/TU:1-2.
- Ricketts, T. H.,E. Dinerstein,D.M Olson;C.J. Loucks (1999). "Terrestrial ecoregions of North America: A conservation assessment" Washington, D.C.: World Wildlife Fund.
- Smith, M. L. and Miller, R. R. (1986). "The evolution of the Rio Grand Basin as inferred from its fish fauna" C. H. Hocutt and E. O. Wiley (Ed.) The zoogeography of North American freshwater fishes ( pp. 457-485 ) New York, New York, USA: Wiley.
- Abell, R.,Olson, D.,Dinerstein, E.,Hurley, P. T.,Diggs, J. T.,Eichbaum, W.,Walters, S.,Wettengel, W.,Allnutt, T.,Loucks, C. J.;Hedao, P. (2000). "Freshwater ecoregions of North America" Washington, D.C.: Island Press.
- Maxwell, J. R., Edwards, C. J., Jensen, M. E., et al. (1995) \A hierarchical framework of aquatic ecological units in North America (Nearctic Zone)\ St. Paul, MN. North Central Forest Experiment Station, USDA Forest Service.