01522oam 2200385 a 450 991069211810332120040131161352.0(CKB)5470000002352257(OCoLC)54207203ocm54207203(OCoLC)995470000002352257(EXLCZ)99547000000235225720040131d2002 ua 0engurgn||||||txtrdacontentcrdamediacrrdacarrierObservations of environmental change in Grand Canyon, Arizona[electronic resource] /by Robert H. Webb, Theodore S. Melis, and Richard A. Valdez ; prepared in cooperation with Grand Canyon Monitoring and Research CenterTucson, Ariz. :U.S. Geological Survey ; Denver, CO :U.S. Geological Survey, Information Services [distributor],2002.Water-resources investigations report ;02-4080Title from title screen (viewed on Jan. 31, 2004).Includes bibliographic references.Grand Canyon (Ariz.)Environmental conditionsHistoryWebb Robert H123725Melis Theodore S1381361Valdez Richard A1381362Grand Canyon Monitoring and Research Center.Geological Survey (U.S.)GPOGPOBOOK9910692118103321Observations of environmental change in Grand Canyon, Arizona3423903UNINA