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Topic
- Rivers 17
- Bodies of water 16
- River engineering 16
- United States. Congress--Records and correspondence 16
- River channels 15
- River surveys 15
- Canals 11
- Northwest, Pacific 11
- Harbors 10
- United States--Armed Forces--Organization--Charts, diagrams, etc 8
- Rapids 7
- Bridges--Design and construction 6
- Conflict management 6
- International regimes 6
- Negotiation 6
- Technology 6
- West (U.S.) 5
- Agriculture 1
- Armed Forces 1
- Droughts 1