Geospatial Analysis of the Lower Colorado River

The history of 20th century changes in the landscape, river flow, climate, and development of the Lower Colorado River offers clues to better understand the environmental processes and conditions needed to maintain populations of native species and ecosystems. Agriculture and development, together with dams and channelization of the river, have brought large, mostly undocumented changes to the ecosystems extending from Lake Mead to the Colorado River delta. Habitats in the LCR change in response to invasive species, urban growth, and public works including water regulation, flood control, flow regulation, and water diversion. These change vectors intermingle with wildlife refuges, parks, agriculture, tribal lands, water-recreation centers, mining districts, and wilderness areas. This patchwork of different ownership and management priorities, combined with severe constraints on the magnitude and timing of flow releases, leaves limited possibilities for management actions that could create positive ecosystem changes. A thorough understanding of how the water, sediment, and ecosystems have responded to past changes would allow better forecasting of how the ecosystems and habitats may respond to alternative future changes.

Our objective is to improve understanding of the history and rates of landscape and ecologic change along the lower Colorado River, and links to geologic and hydrologic processes. We are developing a time series of geospatial data that incorporate repeat photography, aerial photography, Landsat imagery, and mapped data that can be analyzed to document changes in both landscape and vegetation on regional and local scales. Landsat images and GIS techniques are well suited for documenting changes along large sections of the of the river valley. A history of ecosystem changes and their relation to changes in the landscape, river flow, climate, and development will allow an understanding of the environmental processes and conditions needed to maintain populations of native species and ecosystems.

Scientists in the Geography Discipline at the USGS have created a baseline reference map atlas for researchers, available at http://crossborder.arizona.edu/lcr/. Datasets include: the Study Area, 1902 USGS Topographic Maps, 1938 BOR Aerial Photo Mosaics, 1992-1996 USGS Digital Orthophoto Quarter Quadrangles (DOQQ), 1997 BOR Aerial Photos, USGS 100K Digital Raster Graphics (DRG), USGS 250K DRGs, Cities, Places Along the River, Lakes, Rivers, Roads, Counties, and States. In the FY07/08, we propose to maintain the data that is already available at this website with our partners at the Bureau of Reclamation and to continue to access, process (make digital and reference), and provide more map products through this channel. Our focus this year will be to create higher resolution maps at the Cibola and Imperial Wildlife Refuges as a pilot-like study approach that may be extrapolated on for the entire river.

Publications and Websites:

Norman, Laura M., Gishey, Michael, Gass, Leila, Yanites, Brian, Pfeifer, Edwin, Simms, Ron, and Ahlbrant, Ray, 2006. "Processed 1938 Aerial Photography for Selected Areas of the Lower Colorado River, Southwestern United States": U.S. Geological Survey Open File Report 2006-1141. http://pubs.usgs.gov/of/2006/1141.

Norman, Laura M., Webb, Robert H., Gass, Leila, Yanites, Brian, Howard, Keith, Pfeifer, Ed, and Beard, L. Sue, 2004, Geospatial Analysis Of Changes In River-Channel Position And Riparian Vegetation Of The Lower Colorado River: Proceedings, The Geological Society of America Denver Annual Meeting, November 7-10, Paper No. 218-9, Denver, CO. (POSTER)

http://crossborder.arizona.edu/lcr/