1. Groundwater
Groundwater
• Groundwater ---> water stored in open spaces
within underground rocks and sediments.
• More than 65% of the groundwater used in the
U.S. is attributable to agricultural needs.
•
in many places.
> New sources must be found;
> Existing resources must be protected.
> A non-renewable resource in most places
• Capable of shaping the landscape (
> erosion and deposition of silt, clay, and dissolved materials
> forms caves, sinkholes, and speleothems
• Groundwater ---> water stored in open spaces
within underground rocks and sediments.
• More than 65% of the groundwater used in the
U.S. is attributable to agricultural needs.
• Demand has depleted the supply of groundwater
in many places.
> New sources must be found;
> Existing resources must be protected.
> A non-renewable resource in most places
• Capable of shaping the landscape ( Karst )
> erosion and deposition of silt, clay, and dissolved materials
> forms caves, sinkholes, and speleothems
2.
3. Porosity & Permeability
Porosity & Permeability
• Porosity
> that portion of the material's volume which is
pore spaces.
> i.e.
• Permeability
> the ability of a material to transmit fluids.
> i.e.the degree of interconnectedness of
the empty space
• Porosity
> that portion of the material's volume which is
pore spaces.
> i.e.the amount of empty space in rock
or sediments
• Permeability
> the ability of a material to transmit fluids.
> i.e.the degree of interconnectedness of
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
6. Permeability
Permeability
• Materials must have both &
Permeability to allow water to move
through it!
• Materials must have both Porosity
Permeability to allow water to move
through it!
• Styrofoam has high porosity
> this makes it a good insulator
- keeps things hot or cold
• Styrofoam has low permeability
> allows you to keep liquids in it.
> clay has high porosity, but low
permeability-> little water movement
through clay
• Styrofoam has high porosity
> this makes it a good insulator
- keeps things hot or cold
• Styrofoam has low permeability
> allows you to keep liquids in it.
> clay has high porosity, but low
permeability-> little water movement
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
> a porous & permeable layer capable of
transmitting groundwater.
- well rounded, well sorted, sand & gravel.
• Aquiclude (or Aquitard )
> an impermeable layer preventing
movement of groundwater.
- Shales, unfractured Ign & Mm Rxs.
• Aquifer
> a porous & permeable layer capable of
transmitting groundwater.
- well rounded, well sorted, sand & gravel.
• Aquiclude (or Aquitard )
> an impermeable layer preventing
movement of groundwater.
- Shales, unfractured Ign & Mm rock, crystalline
limestone.
14. Confined systems
Groundwater is confined between impermeable
layers (Aquicludes orAquitards) and builds up
hydrostatic pressure.
Water rises to that pressure surface once a well is
drilled.
Groundwater is confined between impermeable
layers (Aquicludes orAquitards) and builds up
hydrostatic pressure.
Water rises to that pressure surface once a well is
drilled.
Many rural communities utilize this principle with
water towers as the municipal water supply.
Many rural communities utilize this principle with
water towers as the municipal water supply.
15.
16. Modifications & Effects on
Groundwater
Modifications & Effects on
Groundwater
•
• Modifications will....
> 1) lower the water table;
> 2) decrease hydrostatic pressure;
> 3) allow saltwater encroachment;
> 4) cause subsidence;
> 5) allow contamination of the groundwater.
• Currently ~20-30% of the water used in the U.S. is
groundwater. Much higher in some places
• Modifications will....
> 1) lower the water table;
> 2) decrease hydrostatic pressure;
> 3) allow saltwater encroachment;
> 4) cause subsidence;
> 5) allow contamination of the groundwater.
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
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.
