1. Water: Humans and Usage

2. Dry Climates Gobi Desert: Historically small annual precipitation Too Little Water

3. Sahara Desert: also little rain

4. Too Little Water Overdraft: H 2 O is withdrawn faster than replaced. Water table falls, wells dry up Will occur when removing more H 2 O than is “recharged” by rain/snowmelt

5. Depleted due to agriculture. Supplies H 2 O to 80% of people living here. Corn and wheat farmers! Good ex of TOC Case Study: Ogallala Aquifer

6. Problems with Aquifer Depletion

7. Subside nce Overdraft causes porous formations to collapse San Joaquin Valley has sunk 10m in 50 years

10. Guatemala City, 2010

11. Ex: Sinkholes Underground cavern or channels collapse Causes death of aquifer

12. Saltwater Intrusion  Salt water = more dense than fresh  Continual fresh water forces back salt water  When fresh water is reduced, salt water can intrude into aquifer.

13. Buildup of salt that never washed away. May render land unfit for crop production if not heavily irrigated. Salinization

15. Cities & Industry Compete heavily with agriculture for water Built Aqueducts to transport water from distances.

16. Discussion: How can we save freshwater? Brainstorm methods to share out!

17. Increasing Water Supplies

18. Distillation: Remove salt from H 2 O by boiling & recondensing (adding cold) Ex: all water in Oman and Bahrain Desalinization

19. Reverse Osmosis: Forces salt water through a membrane impermeable to salt Desalinization

20. 1.Expensive to operate and maintain 2.Large Input of Energy Required 3.Excess salts go where? Probs w/Desalinization

21. Harvesting Icebergs –Carry fresh water to places in need –Economically or environmentally sound?

22. Increasing Water Supplies Seeding Clouds Use dry ice or KI 2 crystals to cause rain to precipitate out of clouds Takes H 2 O out of clouds that would fall elsewhere  drought? –Possible contamination?

23. Where Do We Get Our Water From?

24. Delivery 1: Colorado River Aqueduct Approx. 60 % delivered from river

26. About 30 % delivered from here Snow melt from Sierra Nevada Mtn Range Delivery 2: Los Angeles Aqueduct

28. LA diverts fresh water that should go to Mono Lake  high salinity

30. 10% from here Recharged with LA Rain Delivery 3 : Los Angeles Groundwater