GROUNDWATERGROUNDWATER

Global Distribution of WaterGlobal Distribution of Water

The Hydrologic CycleThe Hydrologic Cycle

Groundwater-Related Terms to RememberGroundwater-Related Terms to Remember

• AquiferAquifer:: a body of rock or soil that stores and easily a body of rock or soil that stores and easily transmits a significant quantity of groundwatertransmits a significant quantity of groundwater– A A confined aquiferconfined aquifer is overlain by an aquitard is overlain by an aquitard– An An unconfined aquiferunconfined aquifer is overlain by the water table is overlain by the water table

• AquitardAquitard:: an impermeable bed that hinders movement of an impermeable bed that hinders movement of

groundwatergroundwater

• Artesian wellArtesian well:: a well in which the groundwater rises to a a well in which the groundwater rises to a level higher than where it was first encountered level higher than where it was first encountered

• Cone of depressionCone of depression:: a cone-shaped depression in the a cone-shaped depression in the water table surrounding a well from which water is water table surrounding a well from which water is pumped faster than it can move through the aquiferpumped faster than it can move through the aquifer

Groundwater-Related Terms to RememberGroundwater-Related Terms to Remember• DrawdownDrawdown:: is the difference in elevation between the is the difference in elevation between the

undisturbed water table and the bottom of a cone of undisturbed water table and the bottom of a cone of depressiondepression

• GeyserGeyser:: a type of hydrothermal spring that intermittently a type of hydrothermal spring that intermittently erupts jets of hot water and steamerupts jets of hot water and steam

• GroundwaterGroundwater:: water in the zone of saturation water in the zone of saturation

• Hard waterHard water:: does not lather readily with soap, due to high does not lather readily with soap, due to high concentration(s) of Ca concentration(s) of Ca 2+2+, Mg , Mg 2+2+, Fe , Fe 2+2+, and/or Mn , and/or Mn 2+2+

• Karst topographyKarst topography:: formed in limestone bedrock in formed in limestone bedrock in response to dissolution of the limestone by acidic waterresponse to dissolution of the limestone by acidic water– Characterized by the presence of caves, sinkholes, Characterized by the presence of caves, sinkholes,

disappearing streams, solution valleys, etc. disappearing streams, solution valleys, etc.

Groundwater-Related Terms to RememberGroundwater-Related Terms to Remember• Perched water tablePerched water table:: unconfined groundwater separated unconfined groundwater separated

from the underlying main body of groundwater by an from the underlying main body of groundwater by an aquitard and a zone of aerationaquitard and a zone of aeration

• PercolationPercolation:: slow movement of water through small slow movement of water through small openings within a porous materialopenings within a porous material

• PermeabilityPermeability:: a measure of the ability of a material to a measure of the ability of a material to transmit groundwater. Dependent upontransmit groundwater. Dependent upon– How many conduits are presentHow many conduits are present– How big the conduits areHow big the conduits are– How straight the conduits areHow straight the conduits are

• Pore spacePore space:: any open space within a body of sediment or any open space within a body of sediment or rockrock

Groundwater-Related Terms to RememberGroundwater-Related Terms to Remember

• PorosityPorosity:: the percentage of a material occupied by pore the percentage of a material occupied by pore spacesspaces

• Primary porosityPrimary porosity:: the spaces between grains composing the spaces between grains composing the rockthe rock

• Secondary porositySecondary porosity:: cracks and caves produced by cracks and caves produced by jointing, faulting, and dissolution of the bedrockjointing, faulting, and dissolution of the bedrock

• SinkholeSinkhole:: a depression formed by collapse of the roof of a depression formed by collapse of the roof of a cavea cave

• SpringSpring:: a flow of groundwater naturally emerging at the a flow of groundwater naturally emerging at the Earth’s surfaceEarth’s surface

Groundwater-Related Terms to RememberGroundwater-Related Terms to Remember

• StalactiteStalactite:: an icicle-like structure attached to the ceiling an icicle-like structure attached to the ceiling of a caveof a cave

• StalagmiteStalagmite:: a conical-shaped structure attached to the a conical-shaped structure attached to the floor of a cavefloor of a cave

• Zone of aerationZone of aeration:: the unsaturated region above the water the unsaturated region above the water table, the region where the pore spaces are filled partially table, the region where the pore spaces are filled partially with air and partially with waterwith air and partially with water

• Water tableWater table:: the top of the zone of saturation the top of the zone of saturation

• Zone of saturationZone of saturation:: the region below the water table, the the region below the water table, the region where the pore spaces are completely filled with region where the pore spaces are completely filled with groundwatergroundwater

Features Associated with Subsurface WaterFeatures Associated with Subsurface Water

Zone of aeration: Zone of aeration: Pore spaces contain Pore spaces contain air and waterair and water

Zone of saturation:Zone of saturation:Pore spaces are Pore spaces are filled with waterfilled with water

Water tableWater table

Perched water tablePerched water table

Formation of a Water Table

Perched Water TablesPerched Water Tables (Plummer, McGeary, and Carlson, 2003, Physical Geology, 9(Plummer, McGeary, and Carlson, 2003, Physical Geology, 9thth ed.) ed.)

Sandstone

SandstoneSandstone

Mudstone

Surface Exposure of the Water TableSurface Exposure of the Water TableThe surface of any sea, lake, pond, stream, or spring is the water tableThe surface of any sea, lake, pond, stream, or spring is the water table

Water table

A Gaining StreamA Gaining Stream

Water table

Note that groundwater flow (blue lines) is always Note that groundwater flow (blue lines) is always perpendicular to the equipotential lines (black lines)perpendicular to the equipotential lines (black lines)

Movement of Movement of GroundwaterGroundwater

During wet weather During wet weather the water table rises, the water table rises,

is rechargedis recharged

During drought During drought the water table fallsthe water table falls

Movement of GroundwaterMovement of Groundwater

Note that the topography of the water table Note that the topography of the water table usually mimics the topography of the landusually mimics the topography of the land

Gaining and Losing StreamsGaining and Losing Streams

A losing streamA losing stream::During droughts During droughts

streams lose waterstreams lose water to to the saturated zonethe saturated zone

In arid regionsIn arid regions:: The topography of the The topography of the

water table does not mimic water table does not mimic the topography of the landthe topography of the land

A gaining stream:During rainy seasons

streams gain water from the saturated zone

Cone of Depression Produced by a Pumping WellCone of Depression Produced by a Pumping Well

Drawdown:Drawdown: is the difference in elevation is the difference in elevation

between the undusturbed water between the undusturbed water table and the bottom of the table and the bottom of the

cone of depressioncone of depression

A A cone of depression: cone of depression: forms in vicinity of a pumped well forms in vicinity of a pumped well

because the groundwater is because the groundwater is pumped out faster than it pumped out faster than it

can move through the groundcan move through the ground

Formation of a Cone of Depression

Primary PorosityPrimary Porosity

PorosityPorosity:: the percent of a material occupied by pore spaces the percent of a material occupied by pore spaces

Primary porosityPrimary porosity: the spaces between : the spaces between the grains composing the rockthe grains composing the rock

Secondary PorositySecondary Porosity

PorosityPorosity:: the percent of a material occupied by pore spaces the percent of a material occupied by pore spaces

Secondary porositySecondary porosity: the cracks and caves produced: the cracks and caves producedby jointing, faulting, and dissolution of the bedrockby jointing, faulting, and dissolution of the bedrock

Effect of Porosity and Permeability on Wells:Effect of Porosity and Permeability on Wells:Mudstone versus SandstoneMudstone versus Sandstone

High porosity,High porosity,low permeabilitylow permeability

High porosity,High porosity,high permeabilityhigh permeability

Effect of Porosity and Permeability on Wells: Effect of Porosity and Permeability on Wells: Fractured versus Un-fractured BedrockFractured versus Un-fractured Bedrock

Unconfined and Confined AquifersUnconfined and Confined Aquifers

ConfinedConfinedaquiferaquifer

ConfinedConfinedaquiferaquifer

UnconfinedUnconfinedaquiferaquifer

ConfinedConfinedaquiferaquifer

Artesian SystemsArtesian Systems

Artesian systems are systems in which groundwater rises Artesian systems are systems in which groundwater rises higher than the elevation at which it was first encounteredhigher than the elevation at which it was first encountered

Flowing Artesian WellFlowing Artesian Well

Salt Water IntrusionSalt Water Intrusion ContaminationContamination

Problems Affecting the Water Table and GroundwaterProblems Affecting the Water Table and Groundwater