1. Water Beneath the Surface
6.3

2. There is Water Underground
Pore spaces + fractures and joints = lots of openings
Water collects underground

3. What happens when it rains?
Runs off, evaporates, soaks into ground
Underground water depends on:
Steepness of slopes
Surface materials
Intensity and duration of rain
Vegetation type
Amount of vegetation

4. Where does the water in the soil go?
Seeps downward until the zone of saturation
Zone of saturation = area where water fills all of the open spaces in sediment and rock
Groundwater is in zone of saturation

5. Water Table Upper limit of zone of saturation Water can be pumped
Above the water table = not saturated = zone of aeration
Wells can’t pump water from zone of aeration

6. Porosity and Permeability
Flow and storage of groundwater depend on material underground
Porosity = percentage of pore spaces (spaces between sedimentary particles)
Permeability = ability to flow
Rock can be porous and not very permeable

7. How does groundwater move?
Twisting and turning through small openings
Moves more slowly when pore spaces are smaller
Too small --> water can’t move
Ex: clay = high porosity but impermeable
Aquifers = transmit groundwater freely
Source of well water

8. Aquifer

9. Springs Spring = flow of groundwater naturally at the surface
water table intersects the ground surface
Hot spring = 6-9 °C hotter than the average annual air temperature

10. Geysers Hot spring where column of water shoots up at intervals
Ex: Old Faithful
Superheated water expands
some water forced out at the surface
Loss of water = decreases pressure
Some water turns to steam
Geyser erupts

11. Wells Hole bored into the zone of saturation
Biggest user: irrigation for agriculture
Must go far below the water table
Cone of depression = withdraw more water than is replenished

12. Artesian Well Most wells need to be pumped in order to get water
Artesian well = groundwater rises on its own under pressure
Water in aquifer that is tilted
Water can’t escape

13. Caverns Limestone = easily weathered by groundwater
groundwater contains carbonic acid
Carbonic acid weathers rock
Cavern = naturally formed underground chamber
Erosion forms most caverns at or below the water table in the zone of saturation
Dissolving process slowly creates cavities and caverns

14. Caverns Stalactites = hang from the ceiling of a cavern
Water seeps through cracks in the cavern’s ceiling
Stalagmites = develop on the floor of the cavern
Water falls from the ceiling and splatters on the floor

15. Karst Topography Underlain by limestone
Evidence of groundwater erosion seen at the surface
US = limestone
Kentucky, Florida, Tennessee, soutern Indiana, Alabama
Lack of streams

16. Sinkholes
Karst areas have sinkholes = depression because groundwater has removed soluble rock
Some happen gradually, some happen suddenly

17. Environmental Problems
Land Subsidence = large amounts of groundwater have been withdrawn
Groundwater supplies are finite
Water pumped from wells faster than it can be replaced
Ground sinks
Ex: California

18. Groundwater Contamination
Sewage from septic tanks, farm wastes, broken sewers
Highly permeable means increase in groundwater contamination
Fertilizers spread across land, pesticides, highway salt

19. What happens if groundwater is polluted?
Abandon the water supply = pollutants flush out gradually
Aquifer unused for years
Pump out and treat polluted water
Aquifer recharges naturally
Prevention