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Lower Colorado River Environmental Conditions - Protected Areas and Managed Waters

Environmental conditions reflect the geography, climate and cultural activities in an area and may be a critical consideration in water resource management and development.  Discussed in this section is vegetation, protection of riparian areas through the Arizona Water Protection Fund Program, threatened and endangered species, public lands protected from development as national monuments, wildlife refuges and wilderness areas, and managed waters.  No instream flow claims (a non-diversionary appropriation of surface water for recreation and wildlife use) have been filed in this planning area.

Click to view Figure 7.0-12

Figure 7.0-12 Wilderness Areas in the Lower Colorado River Planning Area

National Monuments, Wildlife Refuges and Wilderness Areas

The Lower Colorado River Planning Area contains 15 wilderness areas administered by the Bureau of Land Management (BLM), four National Wildlife Refuges (NWR) and two National Monuments (Figure 7.0-12).  Both monuments and three wildlife refuges also contain wilderness areas. In total there are 2.3 million acres of protected federal lands in the planning area, accounting for 21% of the land area.

Eight BLM wilderness areas are entirely within the planning area as well as parts of seven others. Wilderness areas are designated under the 1964 Wilderness Act to preserve and protect the designated area in its natural condition.  Designated wilderness areas managed by the BLM, their size, basin location and a brief description of the area are listed in Table 7.0-2.

The largest protected area in the planning area is the Cabeza Prieta NWR, the third largest refuge in the contiguous United States with an area of over 860,000 acres.  Designated in 1939, it lies within the Lower Gila and Western Mexican Drainage basins and shares a 56-mile border with the Mexican state of Sonora. Most of the refuge is designated as wilderness. The refuge provides habitat for desert bighorn sheep, the endangered Sonoran pronghorn and lesser long-nosed bat, as well as 420 plant species and more than 300 kinds of wildlife. (USFWS, 2007a)  The U.S. pronghorn population is estimated at around 50 animals. 

Cibola NWR straddles the Colorado River, with almost 13,000 acres located in the Parker Basin and the remainder in California.  The refuge was established in 1964 to restore and protect historic habitat and wintering grounds for migratory birds and other wildlife. About 85% of Arizona’s wintering Canadian Goose population is found on the refuge. (USFWS, 2007b)

Kofa NWR, at 665,400 acres, is located in the Lower Gila, Parker and Ranegras Plain basins.  Established in 1939, it provides habitat for desert bighorn sheep, currently numbering 800-1,000 individuals, and protection for the California fan palm, the only native palm in Arizona (USFWS, 2007c).  Most of the refuge is designated as wilderness.

Imperial NWR protects wildlife habitat along 30 miles of the Colorado River in Arizona and California, including the last unchannelized section of the river before it enters Mexico.  The entire refuge encompasses almost 25,800 acres, of which 15,000 acres is designated wilderness.  In Arizona, refuge lands are located in the Lower Gila and Parker basins. Efforts are underway to restore wetlands, control tamarisk, plant cottonwood and willow trees, protect lakes and manage marshlands and croplands to provide food and habitat for wintering migratory birds. (USFWS, 2007d)

Kofa Mountains

Kofa Mountains, Parker Basin

Organ Pipe Cactus National Monument preserves approximately 106,800 acres of relatively intact Sonoran Desert ecosystem in the Lower Gila and Western Mexican Drainage basins.  The Monument contains twenty-six species of cactus and provides habitat for the endangered Quitobaquito Pupfish and Sonoran Pronghorn.  About 95% of the Monument is designated as wilderness.  The United Nations designated the Monument as an International Biosphere Reserve in 1976.   Due to the remoteness of the area, each year thousands of people illegally enter the U.S. through the monument using unofficial roads and trails. This traffic has adversely impacted habitat including deposition of trash, damage to plants, pollution of water sources, and soil erosion. (NPS, 2007)

A portion of the 496,000-acre Sonoran Desert National Monument, established by executive proclamation in 2001, is located in the Gila Bend Basin. The monument contains extensive areas of saguaro cactus forest, and archeological and historic sites. Three wilderness areas are contained within the Monument boundaries. (BLM, 2007)

Imperial National Wildlife Refuge

Colorado River through the Imperial National Wildlife Refuge

Managed Waters

Water management decisions and operations outside of the planning area affect the character of the Colorado River within the planning area. Use of Colorado River water is primarily under the jurisdiction of the federal government and was developed through a number of Congressional acts, Supreme Court Decisions, multi-state compacts and an international treaty collectively known as the “Law of the River.” More detail on management issues affecting the river are found in Section 7.0-8.

Historically, flow in the Colorado River was highly unpredictable with annual variation of 5 maf to 24 maf at its point of discharge to the Gulf of California.  Sediments were carried downstream with spring floods, forming beaches and a large delta where the river met the sea.  These floods often changed the course of the river.  Today the river flow does not always reach the Gulf due to diversions, sediment is trapped behind dams and the river is channelized through parts of its length.

Prior to development, the Colorado River delta area was one of the richest estuaries in the world. Upstream diversions have severely impacted the delta with a small remnant remaining in the Cienega de Santa Clara.  This remnant has been maintained as a result of bypassed saline return flows generated by the Wellton-Mohawk Irrigation and Drainage District.  Salinity standards established by the 1944 Treaty with Mexico require that these return flows can no longer be returned to the river in Arizona. The Cienega was designated as a Biosphere Reserve in 1994 (Tellman and others, 1997).  Discussions are ongoing on how to manage and utilize return flows in the Yuma area while still sustaining the Cienega.



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