G ROUNDWATER Applied Chemistry

I.Groundwater is held in an underground layer of rock or soil called an aquifer, from Latin:  “aqua” meaning “water”  “ferre” meaning “to bring” or “to yield” II.Water Table – the top surface of groundwater A. Depth varies from area to area B.Fluctuates due to seasonal changes and varying amounts of precipitation C.Excessive pumping from the aquifer (wells) can lower the water table

III.Types of aquifers (2) A.Confined aquifer - a water supply is sandwiched between two impermeable layers 1.Also called artesian aquifers because, when a well is drilled into this layer, the pressure may be so great that water will spurt to the surface without being pumped (artesian well) B.Unconfined aquifer – a water supply which has an impermeable layer under it, but not above it 1.This is the most common type

IV.Ogallala aquifer - largest aquifer in the world A.Located in the midwestern United States B.Named after a Sioux Indian tribe C.More than 2 million years old D.Holds about 650 trillion gallons (2,500 trillion liters)! E.Underlies parts of eight states, stretching about 800 miles (1,288 km) from South Dakota to Texas F.Supplies vast amounts of water for drinking and to irrigate the crops in this important agricultural area

V.Threats to Groundwater - Contaminants: When a groundwater source is contaminated, it is very difficult and expensive to clean up – prevention is best! Leaking underground storage tanksIndustrial waste Leaking septic tanksRoad salts Septic tanks with inadequate drain fieldsSome natural contaminants Landfill seepageFertilizer Animal wastePesticides Abandoned wells that are not properly closed