1. A colloquium presentation by: Derrick Hwang
The Water Table
A colloquium presentation by:
Derrick Hwang

2. What is the Water Table?
Water Table: The top zone of soil and rock in which all voids are saturated with water.

3. What is the Water Table?
The level of the water table varies with topography, climate, and seasonal changes.
This picture shows variations based upon seasonal changes

4. What is the Water Table?
Aquifer: An underground layer of permeable rock from which water may be extracted.
Perched Water Table: An aquifer that is formed above the regional water table.

5. How Does the Water Table Affect Us?
Without water, livestock cannot be grown and land cannot be cultivated.
Only 3% of Earth’s water is fresh water; however, humankind has access to only 1% of this fresh water.
The rise and fall of the water table has a very large impact on how and where fresh water can be distributed to the population.

6. The Importance of Equilibrium
High Plains Aquifer (174,000-square-mile area that includes parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming)

7. The Importance of Equilibrium
Water is extracted from the aquifer using a pump that extends beneath the water table.

8. The Importance of Equilibrium
At Equilibrium:
Recharge (water entering) = Discharge (water leaving)
Over-pumping occurs when more water is drawn from the aquifer than is returned.

9. Equilibrium Lost
What happens when the water table drops below the level of the pump?
To obtain water, we will have to wait until the aquifer naturally recharges itself.
If the pump is near a sea coast, over-pumping will allow saline water to seep into the aquifer – mixing with and replacing the original fresh water.
Over-pumping also causes increased soil salinity, which allows for the growth of invasive plants and causes crops to die out.

10. Equilibrium Lost: Northern India
Net loss of 54 cubic kilometers of groundwater per year between 2002 and 2008.
Water table decrease of 10 centimeters per year.
In some areas where the Coca-Cola company has set up factories, the water table is dropping as much as 55 centimeters per year (about inches).

11. Equilibrium Lost: California's Central Valley
In 2002, produced one-twelfth of the nation’s crops.
Now in danger: Over 20 cubic kilometers of groundwater pumped out since 2003.
Twin GRACE satellites obtained this data. GRACE, a joint mission of NASA and DLR, the German aerospace center, is designed to map changes in Earth's gravitational field. The craft can discern movements of groundwater – which often flows away from a region or evaporates after being pumped from aquifers. GRACE detects shifts in water storage indirectly. The two craft orbit the planet along the same path, with one traveling about 200 kilometers ahead of the other. As the first craft in the pair approaches a gravitational anomaly on Earth's surface -- say, a mountain range made of dense rock or a water body -- it is pulled forward in its orbit. After the first craft passes over the anomaly, it is pulled backward. The second craft is simultaneously pulled forward as it approaches the anomaly. The magnitude of subtle changes in distance between the two craft reveals the gravitational anomaly's size.
On average, the water
table here has dropped
23 centimeters per year.

12. Equilibrium Lost: Ogallala Aquifer
In western Kansas and the Texas High Plains – supplies the United States with 1/5 of its agricultural harvest.
The Ogallala Aquifer is being
depleted at an annual volume
of about 18 Colorado Rivers.
90% of the water pumped
is used to irrigate crops.
1/5 of its agricultural harvest – including the corn needed to satisfy the growing biofuel demand. Corn requires a lot of water to grow.
It will take 6,000 years for
the aquifer to be refilled
naturally.

13. Sustainable Solutions for Ogallala
It takes 1,000 gallons of water to produce 1 ton of grain.
Grow crops without groundwater: Eliminate wells and plant crops in harvest residue.
Develop less-thirsty crops: Drought-resistant corn could reduce amount of necessary water by 10 percent. Wheat does not require as much water as corn.
Evapotranspiration Measurement: Determine the minimal amount of water required to keep crops alive.
planting crops in harvest residue: No plowing after harvest… the stubble catches more snow, decreases soil erosion, and decreases evaporation by about an inch annually.

14. Sustainable Solutions
Take shorter showers: a 4-minute shower uses about 30 gallons of water.
Use a dishwasher or washing machine with full loads.
Check faucets and toilets for leaks.

15. Sustainable Solutions
Xeriscaping – replacing thirsty plants with less thirsty ones will save 750-1,000 gallons of water per month.
Fuel-efficiency: 1,700 gallons of water are needed to produce 1 gallon of ethanol.
Education: Producing a typical American Thanksgiving dinner for six people requires over 30,000 gallons of water.

16. Sustainable Solutions
Should the price of water be raised in order to promote water conservation?
The average price of water in the United States is about $1.50 for 1,000 gallons – or about a penny for one gallon of water. Is this a bargain we can keep?
Would eating lower on the food chain have any effect on water usage?
For 300 million Americans, a small reduction in meat, milk, and egg consumption would cut grain use by 30 million tons and water used for irrigation by 300 billion tons.

17. Bibliography
(2009). Water table. Columbia Electronic Encyclopedia, 6th Edition, 1. Retrieved from Academic Search Premier database.
Agricultural Water Table Management Systems, AEX (n.d.). Ohioline. Retrieved March 8, 2010, from
Ground Water Development, Sustaninability, and Water Budgets. (n.d.). USGS Publications Warehouse. Retrieved March 8, 2010, from
Is Your Garden Soil Too Salty?: Salinity Levels Can Affect Plants. (n.d.). Desert/Water-wise Gardens. Retrieved March 8, 2010, from oo_salty

18. Bibliography
Little, J. (2009). Saving the Ogallala Aquifer. Scientific American Earth 3.0, 19(1), Retrieved from Academic Search Premier database.
OECD Glossary of Statistical Terms - Overpumping Definition. (n.d.). OECD Statistics (GDP, unemployment, income, population, labour, education, trade, finance, prices...). Retrieved March 8, 2010, from
Perkins, S. (2010). California hit by irrigation drain. Science News, 177(2), 14. Retrieved from Academic Search Premier database.
Perkins, S. (2009). New data show quickening loss of groundwater beneath India. Science News, 176(6), 5-6. Retrieved from Academic Search Premier database.

19. Bibliography
Water Crisis: How Does it Affect Us? - A precious resource - Softpedia. (n.d.). Latest news - Softpedia. Retrieved March 8, 2010, from shtml
Water Conservation: 25 ways to conserve water in the home and yard. (n.d.). Eartheasy - Sustainable Living. Retrieved March 8, 2010, from
Water Conservation. (n.d.). Mono Lake. Retrieved March 8, 2010, from