6029

• UCREFRP Catalog Number: 6029
• Author: Platania, S. P. and K. R. Betsgen.
• Title: Interim Report on the Fishes of the Lower San Juan River, New Mexico, 1987.
• USFW Year: 1988.
• USFW - Doc Type: Santa Fe, NM.
• Copyright Material: NO

INTRODUCTION
The Colorado River Basin drains portions of seven western
states (Wyoming, Colorado, Utah, Nevada, New Mexico, Arizona, and
California) and approximately 8% of the land surface area of the
United States (Bishop and Porcella 1980). It is unsurpassed as a
source of water for consumptive use, but has a very minor
discharge compared to that of eastern rivers (Pillsbury 1981).
To assist in the administration of water management programs, the
U.S. Congress divided the Basin into roughly equal upper and
lower segments in 1928 (Figure 1).
The Upper Colorado River Basin, which extends 885 km from
north to south and 563 km from east to west, drains 283,600 km2
in southwestern Wyoming, western Colorado, eastern Utah,
northwestern New Mexico, and northeastern Arizona. The primary
lotic systems of this section are the mainstem Colorado, Green,
Yampa, White, Gunnison, Dolores, and San Juan rivers. Several
authors have further subdivided the Upper Basin into three major
hydrologic sub-basins: Upper Mainstem Colorado, Green, and San
Juan (Iorns et al. 1965, Joseph et al. 1977, Carlson and Carlson
1982).
The San Juan Sub-basin is the second largest of the Upper
Colorado River Basin subdivisions and drains 99,200 km2 in
Colorado, Utah, New Mexico, and Arizona. The primary riverine
components in this section are the Dirty Devil, Escalante, and