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INTRODUCTION <br />Public concerns about the Colorado River environment in the Grand Canyon resulted in a <br />Department of Interior decision to implement research studies and develop a data base for <br />long term monitoring of the impacts of variable flow rates from the Glen Canyon Dam. The <br />purpose of this report is to explain how the GCES/GIS (Glen Canyon Environmental <br />Studies/Geographic Information System) data base is being developed and how it can be used <br />in long term monitoring. <br />The objective of the GCES/GIS program is to use a geographically referenced data base to <br />develop an integrated ecosystem-based monitoring program. <br />Development of the GIS is the responsibility of Reclamation (Bureau of Reclamation) as the <br />lead agency. The GCES Office in Flagstaff, Arizona, provides coordination, verification, and <br />integration, and the Denver Office (Remote Sensing and Geographic Information Section) is <br />responsible for technical development. The other participants in this effort include the NPS <br />(National Park Service), USGS (U.S. Geological Survey), Western Area Power Administration, <br />Western Native American groups, U.S. Fish and Wildlife Service, Arizona Fish and Game, <br />and contractors. <br />This report will describe and discuss the following: <br />• The production of the base maps. <br />• The design of the GCES data base. <br />• How information is consolidated into a GIS. <br />• How the GIS can be used in long term monitoring. <br />Background <br />The GCES office was established in 1982 by the Department of the Interior to study the <br />environmental effects of operating the generators at Glen Canyon Dam. Rewinding the <br />generators provides an increase in the electrical energy output for Western consumers. <br />Modifying the generators may promote greater flow fluctuation through the Grand Canyon <br />than in the past. The amount of water that can be released through the powerplant varies <br />from 1,000 to 33,200 ft3/s. A high flow of 90,000 ft3/s occurred during the flood year of 1983. <br />Increasing public concern about the impacts of the abrupt and highly variable flows on the <br />Colorado River environment resulted in the initiation of an EIS (environmental impact <br />statement) and a long-term monitoring program. Effective use of the data requires the <br />development of an integrated and spatially correct data base to evaluate and monitor the <br />impacts. GCES requested the technical expertise of the Remote Sensing and Geographic <br />Information Section, in Denver, to provide the lead in developing the digital data base so it <br />could be updated, analyzed, and displayed through a GIS, making it available to other <br />resource agencies.