2004 Denver Annual Meeting (November 7–10, 2004)

Paper No. 9
Presentation Time: 8:00 AM-12:00 PM


NORMAN, Laura M.1, WEBB, Robert H.2, GASS, Leila1, YANITES, Brian2, HOWARD, Keith3, PFEIFER, Ed1 and BEARD, L. Sue4, (1)Southwest Geographic Science Team, U.S. Geol Survey, 520 N. Park Ave, Ste #355, Tucson, AZ 85719, (2)U.S. Geol Survey, 520 N. Park Avenue, Tucson, AZ 85719, (3)GEO-WRG-NGM, US Geol Survey, Menlo Park, CA 94025, (4)US Geol Survey, 2255 N Gemini Dr, Flagstaff, AZ 86001-1637, rhwebb@usgs.gov

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, flow regulation, and channelization of the river, have brought large changes to the ecosystems extending from Lake Mead to the Colorado River Delta. Old maps and reports, historical photography, aerial photography beginning in the 1930s, and satellite images beginning in the 1970s can be analyzed to document changes in landscape, vegetation and channel position. Image processing and geographic information systems (GIS) analysis of these datasets can help identify and analyze anthropogenic change and natural variation along the river valley.

Habitats along the river are changing in response to flood control, flow regulation, water diversion, land use, and the introduction of nonnative species. Dams, other public works, and urban growth intermingle with wildlife refuges, parks, agriculture, tribal lands, water-recreation centers, mining districts, and wilderness areas. This patchwork of different ownership and management priorities, in combination with severe constraints on the magnitude and timing of flow releases, creates obstacles for overall management of the ecosystem.

The objective of this project is to improve understanding of the history and rates of landscape and ecologic change along the lower Colorado River and of their effects on geologic and hydrologic processes. The datasets allow an analysis of historical changes in the river’s landscape and ecosystems, as well as modeling of the geomorphology of the river valley and related linkages between habitat, ground water, surface water, and sediment. Our goal is to provide reliable information on the geohydrologic framework of the ecosystem landscape in order to assist in management approaches to restoring and conserving habitats. An improved understanding of that framework can help form a basis for evaluating landscape and ecosystem sensitivity and for predicting the effects of future changes and alternative scenarios.