1. Groundwater Groundwater • •
Groundwater ---> water stored in open spaces
Groundwater ---> water stored in open spaces
within underground rocks and sediments.
within underground rocks and sediments. • •
More than 65% of the groundwater used in the
More than 65% of the groundwater used in the
U.S. is attributable to agricultural needs.
U.S. is attributable to agricultural needs. • •
Demand has depleted the supply of groundwater
in many places.
in many places.
>
>
New sources must be found;
New sources must be found;
>
>
Existing resources must be protected.
Existing resources must be protected.
>
>
A non-renewable resource in most places
A non-renewable resource in most places • •
Capable of shaping the landscape (
Capable of shaping the landscape (
Karst )
>
>
erosion and deposition of silt, clay, and dissolved materials
erosion and deposition of silt, clay, and dissolved materials
caves, sinkholes, and speleothems
caves, sinkholes, and speleothems
>
>
forms
forms

3. Porosity & Permeability Porosity & Permeability• •
Porosity
Porosity
>
>
that portion of the material's volume which is
that portion of the material's volume which is
pore spaces.
pore spaces.
>
>
i.e.
i.e.
the amount of empty space in rock
or sediments • •
Permeability
Permeability
>
>
the ability of a material to transmit fluids.
the ability of a material to transmit fluids.
>
i.e.
the degree of interconnectedness of
the degree of interconnectedness of
>
i.e.
the empty space
the empty space

4. Porosity affected by
particle size, particle shape, sorting of particles, amount of material cementing the grains together, fractures in materials, and internal arrangement of particles

5. Typical Porosity values

6. Permeability Permeability • • Materials must have both
Porosity
&
Permeability
Permeability
to allow water to move
to allow water to move
through it!
through it! • •
Styrofoam has high porosity
Styrofoam has high porosity
>
>
this makes it a good insulator
this makes it a good insulator - -
keeps things hot or cold
keeps things hot or cold • •
Styrofoam has low permeability
Styrofoam has low permeability
>
>
allows you to keep liquids in it.
allows you to keep liquids in it.
>
>
clay has high porosity, but low
clay has high porosity, but low
permeability-> little water movement
permeability-> little water movement
through clay
through clay

7. Materials with high porosity AND high permeability
Unlithified (sediment)
Sand
Gravel
Lithified (rock)
Sandstone
fractured limestone
fractured granites

8. Aquifers and Aquicludes Aquifers and Aquicludes• •
Aquifer
Aquifer
>
> a a
porous
porous
&
&
permeable
permeable
layer capable of
layer capable of
transmitting groundwater.
transmitting groundwater. - -
well rounded, well sorted, sand & gravel.
well rounded, well sorted, sand & gravel. • •
Aquiclude
Aquiclude
(or
(or
Aquitard
Aquitard ) )
>
> an an
impermeable
impermeable
layer preventing
layer preventing
movement of groundwater.
movement of groundwater. - -
Shales, unfractured Ign & Mm Rxs.
Shales, unfractured Ign & Mm rock, crystalline
limestone.

10. Water Table
the boundary between saturated (filled) vs unsaturated (unfilled) pore spaces
In unconfined aquifer systems only

14. Confined systems Groundwater is confined between impermeable
layers (
layers (
Aquicludes
Aquicludes or or
Aquitards
Aquitards
) and builds up
) and builds up
hydrostatic pressure.
hydrostatic pressure.
Water rises to that pressure surface once a well is
Water rises to that pressure surface once a well is
drilled.
drilled.
Many rural communities utilize this principle with
Many rural communities utilize this principle with
water towers as the municipal water supply.
water towers as the municipal water supply.

16. Modifications & Effects on Modifications & Effects on Groundwater
Currently ~20-30% of the water used in the U.S. is • •
groundwater. Much higher in some places • •
Modifications will....
Modifications will....
>
>
1) lower the water table;
1) lower the water table;
>
>
2) decrease hydrostatic pressure;
2) decrease hydrostatic pressure;
>
>
3) allow saltwater encroachment;
3) allow saltwater encroachment;
>
>
4) cause subsidence;
4) cause subsidence;
>
>
5) allow contamination of the groundwater.
5) allow contamination of the groundwater.

17. Salt Water Intrusion

18. Ground water related subsidence
ground levels have decreased in elevation due to water withdrawal from aquifers

19. Contamination issues-1: Septic tanks

20. Contamination issues-2: landfills

21. Wetlands and groundwater
Many wetland areas are tied to water by location
e.g., riverine, downslope, lake/sea margins, etc.
Most wetlands are fed in part by groundwater and surface water
e.g., fens, marshes, swamps
Thus groundwater serves to stabilize water levels over longer term, feeding water to the system over extended dry periods, and providing mineralogical nutrients to the biological and geological systems.
Bogs are a unique case, as they are not typically influenced by groundwater outside the perimeter of the wetland area, yet still have groundwater within them.

22. Types of Wetlands
Marshes – areas of land that are frequently to constantly inundated and are characterized by soft stemmed emergent vegetation
Swamps -areas of land that are frequently to constantly inundated and are characterized by woody emergent vegetation
Bogs – a wetland fed almost exclusively by precipitation characterized by excessive peat deposits, acidic conditions, are somewhat nutrient poor, and have a sphagnum moss surface carpet.
Fens – Peat forming wetlands fed by many sources of water/nutrients. Nutrient rich, less acidic, and generally more diverse than Bogs

23. Swamp

24. Marsh

25. Bog

26. Bog- note the boardwalk

27. Fen

28. Hot groundwater-geysers and hot springs

29. Karst landscapes
Created by groundwater and streams dissolving limestone
pseudokarst involves dissolving non-carbonate rock
Enlarges fractures and pore spaces as rock dissolves
Increases flow of water through the system
Triggers more dissolution of limestone.