Rio Grande River Basin

Rio Grande River [Photo:Texas Commission on Environmental Quality]
Rio Grande River
[Photo:Texas Commission on Environmental Quality]

The Rio Grande begins at its headwaters in the San Juan Mountains of Southern Colorado, flows through New Mexico, and forms the international boundary between Texas and Mexico before flowing into the Gulf of Mexico. The Rio Grande Basin includes many different habitats from the mountains and gorges of the upper reaches of the river to the deserts near El Paso, the diverse biota of Big Bend National Park, and coastal barrier islands near the river's mouth.

IMAGE: Map of the Rio Grande River Basin [Image: NBII CSWGCIN]

What are the issues along the Rio Grande?

Historically, the waters of the Rio Grande flowed into the Gulf of Mexico. However, in recent years intermittent and low flows have occurred below the Elephant Butte dam. Competing uses such as irrigation and municipal water demand, increasing human population, drought conditions, and transboundary issues make the management issues of this binational resource complex. Along with water quantity, other important issues in the Rio Grande Basin include threatened and endangered species, water quality degradation, and exotic species introductions.

Find out more about the Rio Grande River Basin and the Rio Grande Fisheries Data Collection and Management Project, a collaborative project between the Central Southwest Gulf Coast Information Node (CSWGCIN), Southwest Information Node (SWIN), and the Fisheries and Aquatic Resources Node (FAR) of the NBII.

Regional Ecosystems

A land of extremes, the Southwest region has incredibly diverse habitats, climate and geography, from snowy mountain peaks to cactus-laden deserts and expansive red rock plateaus. These make up the wide range of ecosystems found in the region, including iconic ecosystems such as the Great Basin; the Colorado and Columbia Plateaus; the Mojave, Chihuahuan, and Sonoran Deserts; the Shortgrass Prairie; and the Rocky and Sierra Nevada Mountains (Source: The Nature Conservancy's GIS Website).

Ecological regions, or "ecoregions," denote areas of general similarity in ecosystems and environmental resources, and are delineated according to their common physical environment and biological characteristics. Ecoregions are a type of spatial classification tool used by scientists, resources managers, and conservation organizations to regionalize biogeographic areas.

The map below displays the six different Level 2 ecoregions within SWIN, according to the Omernik/US EPA Level 2 classification system.

Level 2 Ecoregions of the Southwest

Image: Level 2 Ecoregions of the Southwest [Image: Big Sky Institute, Montana State University]

Cold Deserts, NPS Cold Deserts
Cold deserts are distinguished by their aridity, unique shrub and cactus vegetation, lack of trees, and topography consisting of plains with hills, plains with mountains, and tablelands of high relief.
South-Central Semi-Arid Prairies, USFS South-Central Semi-Arid Prairies
This ecoregion, which comprises the south-central part of North America's Great Plains, is warmer and was once composed of a different mosaic of potential vegetation than the prairie to the north.
Upper Gila Mountains, NPS Upper Gila Mountains
This mountainous ecoregion is part of a chain of Mexican mountains ranges that extend into the southwestern US.
Warm Deserts, NPS Warm Deserts
Warm deserts, found in the southwest region of the US, are arid regions with unique shrub and cactus vegetation and higher average temperatures than the cold deserts to the north.
Western Cordillera, NPS Western Cordillera
The Western Cordillera ecoregion is characterized by rugged, high, mostly forested mountains with some open, wide valleys.
Western Sierra Madre Piedmont Western Sierra Madre Piedmont
This ecoregion spans the US and Mexico. In the US it is also known as the "Sky Islands" or Madrean Archipelago, and is a region of basins and ranges with medium to high local relief.

About Ecoregions

An ecoregion is a land area defined by ecological and geographical boundaries. Ecoregions are delineated according to their common physical environment (soil, climate, landforms) and biological characteristics (plant and animal communities).

Ecoregions are a type of spatial classification tool used by scientists, resources managers, and conservation organizations to regionalize biogeographic areas. This regionalization is done to organize complex natural systems into discrete units with boundaries.

Ecoregion boundaries indicate a change in the physical environment and ecological structure of a geographic area. While the changes may occur abruptly, change can also be gradual. Therefore, it is important to remember that ecoregion boundaries are approximations of areas of biogeographic change.

Ecoregion Classification

Ecoregion classifications are used to facilitate analyses of biological diversity and assist habitat conservation planning efforts. This type of classification aids management efforts because it facilitates coordination across geopolitical borders (county, city, state, and national). There are a number of different types of ecoregion classification systems that have been created by various management organizations (e.g. the Bailey/ US Forest Service system, the Omernik/US EPA classification, and the World Wildlife Fund classification system). The ecoregion classifications differ in the delineation methods and application. This portal uses the Omernik/US EPA ecoregion classification system.

Classification System

Ecoregions are initially grouped broadly (Level 1), and from there are broken down into more narrow ecological assemblages (Levels 2-4). There are 15 Level 1 ecoregions in North America which delineate the major ecological zones within the continent. These 15 ecoregions are further broken down into 52 Level 2 ecoregions which highlight ecological diversity at the sub-continent level. There are approximately 200 Level 3 ecoregions in North America which describe the physical and ecological characteristics of an area at a regional scale. Level 4 ecoregions are the most narrow and describe ecological assemblages at a localized level.

About the Colorado Plateau

Colorado Plateau [Photo: US Bureau of Land Management]
Colorado Plateau
[Photo: US Bureau of Land Management]

The Colorado Plateau is a physiographic region of the Southwest US, roughly centered on the "Four Corners" area of western Colorado, northwestern New Mexico, southeastern Utah, and northern Arizona. Characterized by canyonlands, painted deserts, red rock formations, and mountain peaks, this region has a unique geologic past and a diversity of plant and animal species.

Map of the Colorado Plateau [Image: USGS Southwest Biological Science Center]

IMAGE: Map of the Colorado Plateau [Image: USGS Southwest Biological Science Center]

Colorado Plateau Resources:

Project Highlight

Sage grouse (Centrocercus urophasianus)
Sage grouse (Centrocercus urophasianus)
Credit: Karen Steenhof, USGS

NBII-Great Basin Information Project Photo Catalogue

The Great Basin Information Project provides consolidated and efficient access to information about the Great Basin and the Columbia Plateau Regions of eastern Washington and Oregon, southern Idaho, northern Nevada and Utah, and portions of northeastern California.  Three major plant communities grow in the Great Basin and Columbia Plateau: sagebrush, salt desert shrub, and pinyon-juniper woodlands.  The Great Basin and Columbia Plateau regions comprise a large area of the western United States, approximately 225,674 sq. miles in size.

The NBII Program is administered by the Biological Informatics Program of the U.S. Geological Survey
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