Geology 683 Arizona 308 Mines and mineral resources 231 Groundwater 167 Geology, Stratigraphic 160 Land use, Rural 97 Land titles Registration and transfer 83 Forest management 77 Water-supply 74 Water quality 67 Copper mines and mining 63 Uranium ores 61 Ore deposits 56 Hydrogeology 50 Outdoor recreation 50 Floods 46 Copper ores 43 Hydrology 43 National parks and reserves 41 Water rights 41 Forest reserves 40 Public lands 38 Arizona History 37 Wilderness areas 37 Coconino National Forest (Ariz.) 36 Conservation of natural resources 36 Grand Canyon National Park (Ariz.) 33 Indians of North America 32 Land use 32 Stream measurements 32 Geomagnetism 31 Kaibab National Forest (Ariz.) 31 Groundwater flow 30 Streamflow 30 Geology, Structural 29 Public lands Management 29 Arizona Description and travel 28 Frontier and pioneer life 27 Aquifers 26 Environmental impact statements 25 Groundwater Quality 25 Glen Canyon Dam (Ariz.) 24 Grand Canyon (Ariz.) 24 Arizona Antiquities 23 Manganese ores 23 Petrology 23 Trails 23 Geochemical prospecting 22 Colorado River (Colo.-Mexico) 20 Indian land transfers 20 Indians of North America Antiquities 20 Indians of North America Legal status, laws, etc 20 Real property, Exchange of 20 Sediment transport 20 Sedimentation and deposition 20 Water chemistry 20 Geochemistry 19 Groundwater Pollution 19 National monuments 19 Prescott National Forest (Ariz.) 19 Forest restoration 18 Forests and forestry 18 National parks and reserves Law and legislation 18 New Mexico 18 Plants 18 Volcanic ash, tuff, etc 18 Breccia 17 Igneous rocks 17 Apache National Forest (Ariz. and N.M.) 16 Environmental monitoring 16 Indians of North America Land tenure 16 Land use Planning 16 Paleontology 16 Soils 16 Chiricahua National Monument (Ariz.) 15 Environmental impact analysis 15 Geomorphology 15 Gold mines and mining 15 Public lands Recreational use 15 Riparian ecology 15 Silver mines and mining 15 Sitgreaves National Forest (Ariz.) 15 Soil surveys 15 Subsidences (Earth movements) 15 Water quality management 15 Arizona Geology 14 Historic sites 14 Indians of North America Government relations 14 Tonto National Forest (Ariz.) 14 Wild and scenic rivers 14 Breccia pipes 13 Fossil Creek (Ariz.) Environmental conditions 13 National parks and reserves Management 13 Natural resources 13 Ponderosa pine 13 River sediments 13 Saguaro National Park (Ariz.) 13 Sonora (Mexico : State) 13 Streamflow velocity 13 Ecosystem management 12