Chapter 10 Groundwater

1. Chapter 10 Groundwater

2. Why its important • Provides drinking water for half the world’s population • Major source of the water used by agriculture and industry • Groundwater supplies are threatened by overuse and pollution

3. Groundwater is present EVERYWHERE beneath the surface of the land. Groundwater stays on average as groundwater for hundreds to thousands of years.

4. Zone of Saturation Zone of Aeration Zone of Saturation

5. Water table • Water table lowers or drops during dry periods • Speed of groundwater depends on the slope it is on. And the permeability of the material. (Large grain material versus fine-grained material.)

6. Permeability/Impermeability • Aquifers are permeable layers underground that allows groundwater movement • Aquicludes are impermeable layers Porosities can range from 2% to 50%

7. Dissolution (breakdown) Caves • Caves are formed when groundwater which has carbonic acid dissolves and re-deposits the calcium carbonate in limestone and creates dripstone formations

8. Karst Topography • Sinkholes are produced by the dissolution of limestone/caused by the collapse of a cave • A stream drains into a cave system, continues underground, and leaves a dry valley above, also known as a sinking stream

9. Hard water • Hard water contains high concentration of Ca, Mg, or Fe. This is common in limestone areas. Creates clogged pipes • Water softeners are added to dissolve the ions from the hard water.

10. Springs • Natural discharges of groundwater which can vary from drops of water to a full sized rivers. Many of the lakes in Florida are flooded sinkholes that are fed by karst springs.

11. Temperature of Springs • Average annual temperature of the region it is located in: • Hot Springs: Subsurface hot from recent igneous activity. Geysers – Old Faithful erupts about every hour due to pressure build up.

12. Wells • To produce water they must tap into aquifers • If recharge (refilling of water- rain& runoff) doesn’t keep pace the water table drops, wells run dry. • Overpumping lowers the water table. The difference between the original water table and the lower water table is • called Drawdown

13. Unconfined and Unprotected • Water table aquifers become easily polluted • Confined aquifers are more reliable because they are between aquicludes which protects it from pollution Artesian Well spurts pressurized water from a spring.

14. 6 threats to water supply 1925 • Overuse • Subsidence – sinking of land • Pollution of groundwater • Chemicals • Salt • Radon Uranium in rocks This photo shows the approximate location of maximum subsidence in the United States, The site is in the San Joaquin Valley. Signs on pole show approximate altitude of land surface in 1925, 1955, and 1977. In this case, excessive groundwater pumping allowed the upper soil layers to dry out and compress and compact, which is by far the single largest cause of subsidence. 1955 1977

15. Resources protected • All major pollution sources need to be identified and eliminated • Leaks from storage tanks • Seepage from mine drainage • Seepage of faulty septic systems • Saltwater intrusion • Leaks from disposal sites

16. Questions? • How much water does it take ______ • 1. To make a hamburger? • 2. To make 1 sheet of paper? • 3. To make a cotton shirt? • 4. To get 1 pound of chicken? • A. 1 gallon B. 700 gallons C. 3 gallons • D. 4000 gallons and up E. 50 gallons • F. 500 gallons G. 10 gallons H. 25 gallons

17. Questions? • How much water does it take ______ • 1. To make a hamburger? 4000-18,000 gallons • 2. To make 1 sheet of paper? 4 gallons • 3. To make a cotton shirt? 700 gallons • 4. To get 1 pound of chicken? 500 gallons