Download - Chapter 10 Pages 238-263 - District 196
Ground water focus questions
Where does your drinking water come from?
What factors affect ground water movement and storage?
Is ground water an unlimited resource? How much of the world’s water is fresh water? How much of the world’s water is ground
water?
Ground Water Focus Questions
How do confined and unconfined aquifers compare?
What is polluting our ground water and how can we conserve and protect it?
Where does your drinking water come from?
Ground water In cracks and pore
spaces Not in underground
lakes and streams
Zones Saturated zone = where all
the cracks and pore spaces are filled with water = ground water
Zone of aeration = unsaturated zone = area where there is water and air in the pore spaces and cracks
Water table = upper limit of the saturated zone
Porosity The ability to store water
in pores and cracks. Factors affecting it
Particle shape -- rounded has more pore space than angular
Sorted sediments have more pore space than unsorted
Clay - soaks up the water slowly but holds a surprisingly large amount
Permeability
The ability to transmit water Factors affecting it: 1. Sizes of pores &
cracks 2. Whether pores and
cracks are interconnected
3. Capillarity - water is attracted to clay and resists moving
Unconfined aquifer
Does not have impermeable rock above and below.
Must be pumped out Can be contaminated
from surface spills more easily
Confined or Artesian aquifer
When an aquifer lies sandwiched between two impermeable layers
Water rises in the well under pressure
Ground water flow Ground water movement
is typically feet/day but can be faster in coarse gravel or limestone
It may take years, decades or even centuries for groundwater to move long distances through some aquifers.
Ground-water may take only a few days or weeks to move for a short distance through loose soil.
Recharge
Precipitation and runoff enter permeable rock and sediment to recharge the groundwater.
Pavement prevents recharge
Wells - cone of depression
Water use can lower the water table
In coastal areas, this can cause salt water to intrude
Too much water use and too little recharge can lead to subsidence The ground sinks
What is polluting our ground water and how can we conserve and protect it?
Homework: Visit scorecard.org
Enter your zipcode Gather information on
Dakota County 1. Who are the top polluters? 2. What chemicals the main
chemicals released? 3. Where is the superfund
site and what toxins is it releasing?
4. 3 other facts of interest
Observe the poster of nitrates in wells in the Hastings area.
How many wells have over 10 ppm?
Why is this unsafe?