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- Maps 5
- Water-power 3
- Bodies of water 2
- Conservation of natural resources 2
- Northwest, Pacific 2
- Rivers 2
- Water resources development 2
- West (U.S.) 2
- Agriculture 1
- Fisheries 1
- Forests and forestry 1
- Harbors 1
- Hydroelectric power plants 1
- Irrigation projects 1
- Mineral industries 1
- National parks and reserves 1
- Photography 1
- Renewable energy sources 1
- River engineering 1
- Salmon fisheries 1