   Chapter 10
   Pages 238-263

   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?

   How do confined and unconfined aquifers compare?
   What is polluting our ground water and how can we conserve and protect it?

NATURAL RESOURCES II: WATER RESOURCES

ANNUAL MOVEMENT OF WATER ON THE GLOBE

Where’s the Water?
Water on Land
(Where is most of this held?)

   Ground water
   In cracks and pore spaces
   Not in underground lakes and streams

GROUNDWATER

   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

   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

   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

   Aquifers are both porous and permeable.

   Does not have impermeable rock above and below.
   Must be pumped out
   Can be contaminated from surface spills more easily

   When an aquifer lies sandwiched between two impermeable layers
   Water rises in the well under pressure

AQUIFERS AND AQUITARDS

GROUNDWATER FLOW
Surface of the Water Table mimics the topography of the land surface

   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.

   Precipitation and runoff enter permeable rock and sediment to recharge the groundwater.
   Pavement prevents recharge

   Are fed by ground water

Artesian
Conditions
Created by the tilt of a confined aquifer

SPRINGS
Where the land surface abruptly intersects the water table

CAVES and
KARST
Limestone dissolved by acidic groundwater near the top of the water tables

GROUNDWATER HAZARDS

   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

IS GROUNDWATER
A RENEWABLE,
NONRENEWABLE,
OR UNLIMITED
RESOURCE?

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?

   Jim Miller, Associate Professor of Geology,
University of UMD
   http://www.d.umn.edu/~mille066/ teaching.htm