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Subject
- Geology500
- Groundwater388
- Roads303
- Aquifers288
- Harbors171
- Water table142
- Great Britain. Colonial Office128
- Geology, Structural85
- Geology, Stratigraphic83
- Wildfires65
- Hydrogeology62
- Mines and mineral resources57
- Fires54
- Natural disasters54
- Great Britain. Army53
- Floods50
- Fortification46
- Water quality42
- Earthquakes41
- Water-supply38