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

US Water Use

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

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

Aquifers and Recharge Rate

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

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

Sinkholes Subsidence: Sinking of land when groundwater is depleted

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

What Can YOU Do? _________________

Threats to Our Water Supply Pollution: sewage, industrial waste, landfills, and agricultural chemicals

Water Pollution Pathogens Chemicals Sewage Sediment Thermal Pollution Radioactivity

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

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

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

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

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

Point and Nonpoint Sources Urban streets Suburban development Wastewater treatment plant Rural homes Cropland Factory Animal feedlot POINT SOURCES Fig. 22-4 p. 494

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. 20-11, p. 542

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. 20-12, p. 543