Across
- 3. A long period of time without any rainfall
- 4. Take out
- 7. A system formed by the interactions of a community
- 10. A layer of rock
- 12. The waste matter that passes through drains
- 13. A structure built across a river to control the river's flow
- 14. It is a lake
- 17. osmosis To make seawater into freshwater
- 19. unicellular of multicellular organisms, seaweed
- 21. Removing the dissolved salt from ocean water
Down
- 1. Impure, open to dangerous substance
- 2. Supply dry land with water through streams
- 5. Is something that is supplied by nature
- 6. Poisonous substances
- 8. Deep holes
- 9. A channel built to transfer water
- 11. Trustworthy
- 15. long-term plans
- 16. concentrated seawater by-products
- 18. Getting too large
- 20. A source of energy that is not depleted by us