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Background Prior to the construction of Glen Canyon Dam, the ecosystem supported by the Colorado River through the Grand Canyon was dramatically different. The pre-dam Colorado River carried a heavy load of sediment, and seasonal water temperatures ranged from 40 to 80 °F. Annual flooding levels of 100,000 or more cubic feet per second (ft3/s) scoured and redeposited sediment throughout the Canyon. Post-dam water flows from the depths of Lake Powell were relieved of their sediment load upstream and cooled to a relatively constdnt 46 °F. The dam-controlled flow rate varies from an average minimum of 5,000 ft3/s to an average maximum of 30,000 ft3/s in response to daily hydropower demands. In 1982, in reaction to public and scientific concerns about the impact of the Glen Canyon Dam operation on the Canyon's resources, the GCES (Glen Canyon Environmental Studies) were initiated. The GCES program is a coordinated group of agencies, designed to be an integrated, ecosystem-based research and monitoring program. This multi-agency approach to resource evaluation is orchestrated by Reclamation (Bureau of Reclamation). The primary purpose of the GCES is to scientifically quantify the environmental impacts of Glen Canyon Dam operations on the resources of the Colorado River in the Grand Canyon. Among the concerns are beach erosion, invasion of exotic species of plants and animals, decline of native fish species, endangered species, disturbance of archeological and cultural sites, changes in water quality, and economic impacts of redefining operations. These concerns are examined, and modifications in dam management are proposed, in the U.S. Department of the Interior publication, Operation of Glen Canyon Dam: Final Environmental Impact Statement (1995). As part of a long-term monitoring effort, a GIS (geographic information system) data base was proposed as a consolidating tool to allow for integrating data and assessing the impacts of variable flows on Grand Canyon resources. The GIS functions as a visual and analytical tool, as well as an archival device to facilitate data storage, access, and retrieval. The coordination of the long-term monitoring program and research is under the guidance of the GCES office and Dr. Duncan Patten. Long-term monitoring will be built around specific objectives established by the resource agencies, tribes, and resource managers. Additional applied research will be developed around specific, testable hypotheses necessary to interpret monitoring information. Data management will be designed around the existing GCES scientific data management program and the other Colorado River basin data bases. This system will allow data to be compared, analyzed, and maintained in an ecosystem-based approach for future management. Objectives The first and primary objective of this report is to review the development and completion of the GCES/GIS base map products being used in the GCES research and monitoring. By applying the available data in an analysis environment, the pilot study was used to define the specific program objectives: 2