groundwater and subsidence groundwater and subsidence
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Groundwater and
Subsidence
Groundwater and
Subsidence
Groundwater Subsidence Objectives:
• to use principles of groundwater flow and determine if various areas are affected by environmental pollution
• to correlate groundwater withdrawal and land subsidence with routine human practices
Groundwater Subsidence Objectives:
• to use principles of groundwater flow and determine if various areas are affected by environmental pollution
• to correlate groundwater withdrawal and land subsidence with routine human practices
Land Subsidence: The sinking of land or “settling” due to the extraction materials
Land Subsidence: The sinking of land or “settling” due to the extraction materials
In-proper soil compaction inthe year 1173 led to the“leaning” tower of Pisa
“air” in the soil void spaces forced out
creating subsidence
In-proper soil compaction inthe year 1173 led to the“leaning” tower of Pisa
“air” in the soil void spaces forced out
creating subsidence
Subsidence – removal of a coal bedSubsidence – removal of a coal bed
What if groundwater is removed from the subsurfaceWhat if groundwater is removed from the subsurfaceFactors affecting groundwater Factors affecting groundwater subsidencesubsidence
What if groundwater is removed from the subsurfaceWhat if groundwater is removed from the subsurfaceFactors affecting groundwater Factors affecting groundwater subsidencesubsidence
Porosity:Porosity: the amount of voidthe amount of void
spaces available to spaces available to store waterstore water
Expressed as a %Expressed as a %
Porosity:Porosity: the amount of voidthe amount of void
spaces available to spaces available to store waterstore water
Expressed as a %Expressed as a %
10% -20%10% -20%
30%-50%30%-50%
Permeability:Permeability:the ability for water to movethe ability for water to move
(transmit) through the media (transmit) through the media
Permeability:Permeability:the ability for water to movethe ability for water to move
(transmit) through the media (transmit) through the media
Rock Type PorositiesRock Type Porosities
Well sortedsandstone and gravel
Well sortedsandstone and gravel
HighHigh
ClayClayHigh
“hard togive up”
High“hard togive up”
Poorly sortedsands
Cementedsands
Limestone
Shale
Poorly sortedsands
Cementedsands
Limestone
Shale
LowLow
Typical stratgraphic section of theSan Joaquin Valley
Typical stratgraphic section of theSan Joaquin Valley
SandstoneSandstone
Sandstone / siltstoneSandstone / siltstone
Sandstone / siltstone / shaleSandstone / siltstone / shale
19151915
19601960
What will happen when groundwater is removed???What will happen when groundwater is removed???
Example of Land SubsidenceExample of Land Subsidence
300300
600600
12001200
18001800
24002400
Pumping groundwaterfrom 1934 - 1967Pumping groundwaterfrom 1934 - 1967
Line of equal elevationof land subsidenceUnits of millimeters (mm)
Line of equal elevationof land subsidenceUnits of millimeters (mm)
300
600
1,200
1,800
2,400
San Francisco Bay
Silver CreekFault
Line of equal long-termland subsidence (1934-67)(intervals of mm) A
A’1,200
2,400
300300
600600
900900
1,2001,200
1,5001,500
1,8001,800
2,1002,100
2,4002,400
AA A’A’
Vertical ScaleVertical Scale Profile ConstructionProfile Construction
Groundwater: accumulation of water below the surface through infiltration processes
Groundwater: accumulation of water below the surface through infiltration processes
GroundwaterGroundwater
Infiltration into the soilInfiltration into the soil
Groundwater Contamination
• groundwater is contaminated by outside sources that infiltrate through the subsurface
• petroleum (gasoline)• agriculture products• mine waste• dump waste
Groundwater Contamination
• groundwater is contaminated by outside sources that infiltrate through the subsurface
• petroleum (gasoline)• agriculture products• mine waste• dump waste
Migration of groundwater (movement) usingflow linesMigration of groundwater (movement) usingflow lines
water table contour lineswater table
contour lines
GW flow lines
Flow lines always flow perpendicular tocontour lines !!!!!!!Flow lines always flow perpendicular tocontour lines !!!!!!!
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