WSP01461

• File Number: 8549.800
• Description: Rio Grande Basin-Miscellaneous Small Projects and Project Studies-Rio Grande Assessment
• State: CO
• Basin: Rio Grande
• Water Division: 3
• Date: 2/1/1981
• Author: Brandes Kier Stecher
• Title: Water Resources Reference Base for the Assessment of the Rio Grande Region
• Water Supply Pro - Doc Type: Report/Study

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STUDY AREA

The Rio Grande Region, i.e. Water Resources Region 13 as designated by
WRC [3], is defined as the study area for the 13(a) assessment. It includes
all of the land areas in the United States encompassed within the watershed
of the Rio Grande and its major tributary, the Pecos River. The extent of
the study area is indicated in Figure 1. Just over half of the Region is in
New Mexico with about 40 percent in Texas and six percent in Colorado.

The headwaters of the Rio Grande originate on the eastern slopes of the
Continental Divide in a basin formed by the San Juan and the Sangre de Cristo
ranges of the Rocky Mountains in Colorado. The River flows south the full
length of New Mexico to enter Texas near the city of E1 Paso. From there, it
flows generally in a southeasterly direction for 1,244 miles, forming the
international boundary between the United States and Mexico until it reaches
the Gulf of Mexico near Brownsvil1e, Texas. Approximately 335,000 square
miles are included within the boundaries of the watershed [14], of which,
only about half actually drains to the Rio Grande. The remaining lands are
located within closed basins and do not contribute direct runoff to the
River. The actual drainage area of the entire River (176,333 square miles at
Brownsvi11e) is about equally .divided between Mexico and the United States.

The largest tributary in the Region is the Pecos River which rises in
north-central New Mexico, flows south into Texas, and then southeasterly to
join the Rio Grande near Langtry, Texas. The Pecos drains about 35,000
square miles of watershed. Other principal tributaries of the Rio Grande in
the study area are the Rio Puerco (7,350 square miles) and the Rio Chama
(3,144 square miles) in New Mexico and the Devils River (4,035 square miles)
in Texas.

The extreme lower part of the Rio Grande Basin, below La Joya, Texas,
is confined by levees maintained by the International Boundary and Water
Commission (IBWC). Flood waters in the Rio Grande are diverted into f1ood-
ways which discharge into the Gulf through Laguna Madre north of the mouth

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