A colloquium presentation by:Derrick Hwang

The Water Table

Water Table: The top zone of soil and rock in which all voids are saturated with water.

What is the Water Table?

The level of the water table varies with topography, climate, and seasonal changes.

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.

What is the Water Table?

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.

How Does the Water Table Affect Us?

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

The Importance of Equilibrium

The Importance of Equilibrium

Water is extracted from the aquifer using a pump that extends beneath the water table.

The Importance of Equilibrium

Over-pumping occurs when more water is drawn from the aquifer than is returned.

At Equilibrium:Recharge (water entering) = Discharge (water leaving)

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.

Equilibrium Lost

Net loss of 54 cubic kilometers of groundwater per year between 2002 and 2008.

Water table decrease of 10 centimeters per year.

Equilibrium Lost: Northern India

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.On average, the water table here has dropped23 centimeters per year.

In western Kansas and the Texas High Plains – supplies the United States with 1/5 of its agricultural harvest.

Equilibrium Lost: Ogallala Aquifer

90% of the water pumped is used to irrigate crops.

It will take 6,000 years forthe aquifer to be refilled naturally.

The Ogallala Aquifer is beingdepleted at an annual volumeof about 18 Colorado Rivers.

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.

Sustainable Solutions for Ogallala

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.

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.

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.

Sustainable Solutions

(2009). Water table. Columbia Electronic Encyclopedia, 6th Edition, 1. Retrieved from Academic Search Premier database.

Agricultural Water Table Management Systems, AEX 321-97. (n.d.). Ohioline. Retrieved March 8, 2010, from http://ohioline.osu.edu/aex-fact/0321.html

Ground Water Development, Sustaninability, and Water Budgets. (n.d.). USGS Publications Warehouse. Retrieved March 8, 2010, from http://pubs.usgs.gov/circ/circ1186/html/gw_dev.html

Is Your Garden Soil Too Salty?: Salinity Levels Can Affect Plants. (n.d.). Desert/Water-wise Gardens. Retrieved March 8, 2010, from http://desertwaterwisegardens.suite101.com/article.cfm/is_your_garden_soil_too_salty

Bibliography

Little, J. (2009). Saving the Ogallala Aquifer. Scientific American Earth 3.0, 19(1), 32-39. 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 http://stats.oecd.org/glossary/detail.asp?ID=1979

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.

Bibliography

Water Crisis: How Does it Affect Us? - A precious resource - Softpedia. (n.d.). Latest news - Softpedia. Retrieved March 8, 2010, from http://news.softpedia.com/news/Water-Crisis-How-it-Does-Affect-Us-71148.shtml

Water Conservation: 25 ways to conserve water in the home and yard. (n.d.). Eartheasy - Sustainable Living. Retrieved March 8, 2010, from http://www.eartheasy.com/live_water_saving.htm

Water Conservation. (n.d.). Mono Lake. Retrieved March 8, 2010, from http://www.monolake.org/about/waterconservation

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