Newly discovered wetlands of the Andrade Mesa

   The wetlands are in the northern Colorado River delta near the Andrade Mesa, east of Drop 3 where the proposed lining will end. Although the wetlands may have been present as early as 1901, since the first gravity canals were placed across the Andrade Mesa, these wetlands had not been deemed important until their recent discovery from an aerial survey of the delta on June 3, 2002. The survey was followed by a second aerial survey on June 18, 2002, and by several ground-truthing expeditions to determine vegetation types and bird species. They support high-quality bird habitat including sensitive, endangered and locally rare species.

   Currently, the All American Canal is not lined, which means that a portion (2%) of the 300 m3/sec of water flowing through the Canal is currently lost to seepage. Most of this is pumped up foragriculture in Mexico, but a small amount, west of the pumped area, supports this group of wetlands known as Las Pangas in Mexico. There are nearly 20 separate wetland areas, totaling an area of nearly 6,200 ha, with the smallest wetland at ~111 ha and the largest at ~3,025 ha. Approximately 3,500 ha of the total wetland area is east of the proposed lining of the Canal, and would therefore be adversely impacted by this project. There are three main types of habitat: marshes (18%), consisting of open water surface and emergent vegetation; playas (31%), consisting of dry, alkaline lakebeds that are mixtures of bare and vegetative cover; and dunes (51%), consisting of vegetation cover at approximately 58% inside the wetlands compared to only 6% outside the wetlands.

   These wetlands were not mentioned in the 1994 ESA although they are only a few miles from the canal in Mexico. Feel free to contact Osvel, osvel@email.arizona.edu, if you want more information about the birds and ecological value of this habitat. For maps and photographs of the region, please contact Pamela Nagler, pnagler@ag.arizona.edu.