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Topic
- Dams 135
- Rivers--Oregon 101
- Salmon 50
- Fishes--Conservation 35
- Flood control 32
- Lectures and lecturing 31
- Inland water transportation 14
- Water--Pollution 11
- Irrigation 8
- Fishways 7
- Izaak Walton League of America 6
- Lakes--Oregon 6
- Fish hatcheries 5
- Fishing 4
- Oregon Audubon Society 4
- Reservoirs 4
- Beavers 3
- Birds--Conservation 3
- Conservation of natural resources 3
- Oregon Wildlife Federation 3