1. Water Resources

2. Usable Water is Rare

3. Groundwater
Exists in pores (tiny spaces) within permeable rocks called aquifers
Unconfined aquifers: water can easily flow in and out (ex. Rock covered by soil)
Confined aquifers: impermeable layers surround aquifer, impeding water flow
Water table: uppermost level at which water saturates rock – the ‘surface’ of groundwater
Not the ‘water table’ I’m talking about 

4. Groundwater

5. Groundwater
Groundwater Recharge: water from precipitation percolates downward and adds to aquifer
Cannot recharge a confined aquifer unless there is an opening in the impermeable layer – recharge area

6. Groundwater Aquifers provide water for organisms
Plant roots draw water up
Springs: water from aquifer comes out at surface
Dig wells down to aquifers
Use pumps to work against gravity
Artesian wells: confined aquifers under pressure, digging a well forces water up on it’s own

7. Groundwater Age of aquifer water / rate of recharge varies
Unconfined aquifers (1 wk-1 yr) more likely to be contaminated with chemicals released by human activities than confined (10,000-20,000 yrs)
Confined aquifers get used up faster (Ogallala aquifer)
Cone of depression: wells withdraw water, depressing water table
Saltwater intrusion: wells near coast draw saltwater into freshwater table

10. Surface Water Rivers/streams
World’s largest rivers by volume: Amazon, Congo, Yangtze
Humans settled near rivers – transportation and fertile ground (floodplains)

11. Surface Water Ponds/lakes
Filled by precipitation, runoff, and groundwater flowing onto surface – depressions formed by tectonic activity or glaciation
Oligotrophic: low productivity/nutrients
Mesotrophic: medium productivity/nutrients
Eutrophic: high productivity/nutrients

12. Surface Water Wetlands
Absorb excess water, release it slowly, reducing flooding
Saltwater mangrove swamps act as storm barricades
Largest: Pantanal in S. America, Florida Everglades

13. Atmospheric Water
Tiny but important percentage – rainfall distributes water around globe
Droughts: prolonged periods without rain
Can be worsened by human activity
Kill organisms
Disrupt nutrient cycling in soil
“Dustbowl” conditions – dry soil blows away
Hard, impermeable soil prevents water table recharge

14. Atmospheric Water Human activity increases risk of flooding
Impermeable/impervious surfaces, such as pavement, prevent ground from soaking up water in storms

15. Checkpoint:
What are the primary repositories of freshwater on Earth? Which is largest?
What is the difference between a confined aquifer and an unconfined aquifer? How do their recharge rates differ?
How do human activities worsen the effects of floods and droughts?

16. Altering the Availability of Water
Some parts of Earth have less access to water
Humans have invented a variety of methods to divert water from one place to another

17. Levees
Enlarged bank built up on each side of a ricer to prevent flooding
Humans build on floodplains, fertile soil – but don’t want to be flooded
No more fertile sediment added
Levees prevent floods at one location, but make floods worse beyond them
New Orleans, Katrina

18. Dikes Similar to levees, built along ocean coasts
Often combined with pumps to remove excess water

19. Dams Barrier that runs across a river/stream to control water flow
Water stored behind dam in reservoir
Hold water for consumption(40%), electricity generation (3%), flood control (18%), and recreation (38%)

20. Problems with Dams People behind dam forced to relocate
Disruption of natural water flow to which organisms have adapted (ex. Migrating fish)
Fish ladders: help fish bypass dams
Some ecosystems depend on seasonal flooding

21. Aqueducts
Canals or ditches used to carry water from one location to another
Modern ones are enclosed to prevent evaporation
New York and LA depend on aqueducts
Problems:
Construction is expensive/disruptive to ecosystems
Decreases water at the source (can have international impacts)

22. Desalinization Removing salt from saltwater for water-poor countries
Distillation
Water is boiled, salt remains behind, vapor collected and condensed
Very expensive
Reverse osmosis
Saltwater passed through thin semi-permeable membrane – water can pass, salt cannot
Produces very salty liquid, called brine – disposal can harm local ecosystem

24. Checkpoint
How do levees, dikes, dams, and aqueducts differ? What is the primary purpose of each?
Why is it necessary to desalinize water? How does each method work? Which is more cost-effective?

25. Water Uses: Agriculture
70% of world’s freshwater
Irrigation:
Furrow irrigation: trenches dug between crop rows, water fills in
Flood irrigation: entire field flooded at once
Spray irrigation: like giant sprinklers
Drip irrigation: hose w/ holes drips directly onto plants

27. Hydroponic Agriculture
Cultivation of a crop in greenhouse conditions with their roots immersed in a nutrient-rich solution, but no soil
Crops need less water, grown in ideal conditions year-round, with little to no pesticide

28. Water Uses: Industry
Generation of electricity, cooling machinery, refining metals/paper
Some processes do not use up water (turning turbines in dams) while others do (thermoelectric power plants releasing steam)

29. Water Uses: Households
Varies heavily from country to country
Average US citizen uses 157 gallons/day, average Kenyan uses 11 gallons/day

30. Water Uses: Households
Flushing toilets, bathing, laundry, cooking/drinking, washing dishes, watering lawns, washing cars, filling swimming pools
Over 1 billion people in the world lack access to clean drinking water

31. Checkpoint What are the dominant water uses by humans?
How do different irrigation methods influence water use?
What are the biggest steps you can take to reduce water wastage in your own home?

32. Water Ownership
Having the right to use water is not the same as owning it
Many disputes arise over who gets the water
India vs. Bangladesh

33. Water Conservation Water is finite and must be shared
Designing more efficient appliances
Ex. Dual-flush toilets: two buttons, one uses 6 L for solid waste, other only uses 3 L, for liquid waste
Designing more efficient manufacturing equipment
Rainwater collection from impervious surfaces
Wastewater for irrigation

34. Is the Water in Your Toilet Too Clean?
The water in your toilet has been treated to drinking water safety standards, while water draining from your tub or washing machine is treated like sewage
Gray water: wastewater from baths, showers, bathroom sinks, and washing machines
No one wants to drink it, but it is suitable for watering lawns, washing cars, flushing toilets