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Topic
- Deserts 15
- Agriculture 7
- Groundwater 5
- Irrigation 5
- Reclamation of land 5
- Hydrology 4
- Building 3
- Technology 3
- Watersheds 3
- Aquifers 2
- Bureaucracy 2
- Canals 2
- Economics 2
- Politics and government 2
- Sediments (Geology) 2
- Sewage 2
- Water quality 2
- Water-power 2
- Aquaculture 1
- Arid regions 1
