1. Water and the Environment
Warm-up: What do you think is the biggest threat to our groundwater?
REMINDER!!!!
Chapter 10 Study Guide due TOMORROW

2. US Water Use

3. Threats to Our Water Supply
Overuse: pumped out greater rate than the recharge rate

4. Discharge area: area where groundwater is leaving an aquifer
Recharge area: infiltrating rain, snowmelt or surface water enters and replenishes the ground water stores

5. Aquifers and Recharge Rate

6. Saltwater Intrusion
Movement is generally from land freshwater groundwater to ocean’s saltwater

7. Saltwater Intrusion
Groundwater pumping reduces freshwater flow towards coastal discharge areas, causing saltwater to be drawn toward the freshwater zones of the aquifer

8. Sinkholes
Subsidence: Sinking of land when groundwater is depleted

9. What Happens If the Well Goes Dry?
Discuss alternatives, recycle is best

10. What Can YOU Do?
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11. Threats to Our Water Supply
Pollution: sewage, industrial waste, landfills, and agricultural chemicals

12. Water Pollution Pathogens Chemicals Sewage Sediment Thermal Pollution
Radioactivity

13. Groundwater Contamination
When man-made products such as gasoline, oil, road salts and chemicals get into the groundwater and cause it to become unsafe for human use

14. Arsenic
A naturally occurring chemical found in rocks in the earth’s crust
Arsenic is also a poison and cancer causing substance

15. Arsenic Groundwater Contamination
Natural Sources – volcanoes, erosion of rock, forest fires
Man-made Sources – industrial waste and mining activities

16. Maximum Contaminant Level
Standards set by EPA for drinking water quality
MCL (Maximum Contaminant Level) – the upper limit on the amount of substance allowed in public water systems under the Safe Drinking Water Act
Maximum Contaminant Level Goal (MCLG) concentration measured in mg/L

17. Point vs Non-Point Pollution
Point-source – single identifiable source of pollution.
Oil refinery
wastewater discharge outlet
Single farm runoff
Sewer
Non-Point source– area source, not a single point.
Wind erosion of coal piles
Road runoff
Bacteria and nutrients from livestock and pet wastes

18. Point and Nonpoint Sources
Urban streets
Suburban development
Wastewater treatment plant
Rural homes
Cropland
Factory
Animal feedlot
POINT SOURCES
Fig p. 494

19. Hazardous waste injection well Pesticides and fertilizers
Polluted air
Hazardous waste injection well
Pesticides and fertilizers
Deicing road salt
Coal strip mine runoff
Buried gasoline and solvent tanks
Gasoline station
Cesspool, septic tank
Pumping well
Water pumping well
Waste lagoon
Sewer
Landfill
Accidental spills
Leakage from faulty casing
Figure 20.11
Natural capital degradation: principal sources of groundwater contamination in the United States (Concept 20-3A). Another source is saltwater intrusion from excessive groundwater withdrawal in coastal areas. (Figure is not drawn to scale.) Question: What are three sources shown in this picture that might be affecting groundwater in your area?
Discharge
Unconfined freshwater aquifer
Confined aquifer
Confined freshwater aquifer
Groundwater flow
Fig , p. 542

20. Free gasoline dissolves in groundwater (dissolved phase)
Leaking tank
Aquifer
Bedrock
Water table
Figure 20.12
Natural capital degradation: groundwater contamination from a leaking gasoline tank. As the contaminated water spreads from its source in a widening plume, it can be extracted by wells used to provide water for drinking and irrigation.
Groundwater flow
Free gasoline dissolves in groundwater (dissolved phase)
Gasoline leakage plume (liquid phase)
Migrating vapor phase
Water well
Contaminant plume moves with the groundwater
Fig , p. 543