Rephotography along the Salt and Gila Rivers in Maricopa County, AZ between Granite Reef Dam and Gillespie Dam (1895-1999)

Scanned black-and-white photographic images for the Salt and Gila Rivers in Maricopa, County, Arizona, between Granite Reef Dam and Gillespie Dam at 77 sites. Some sites lack images (they are known to exist, but the imagery is not useful). For each site, there is at least one historical image that starts the series, and then one, two, or three subsequent images that are re-photographs of the original sites decades later. The original images are from as early as the 1890s, but the majority are from the 1940s. Repeat photographs are from the 1980s and 1990s. Many of the original images are from U.S. Army Corps of Engineers flood project surveys in the 1940s. The images show changing conditions in and along the main river channels, documenting ecosystem adjustments in vegetation, geomorphology, and surface hydrology. Some images document change in the built environment in and near the rivers. In some cases, particularly in the central urban area, sites have become so altered that it is impossible to relocate the exact spot of the original image. At these sites the location of repeat images changed 10 m or less; in fewer than 5 cases modern construction obliterated the original site. GPS was not available at outset of the project, so that positions were located by alignment of landmarks and landscape features.