Chapter 17: Groundwater. Distribution of Fresh Water

Chapter 17: GroundwaterChapter 17: Groundwater

Distribution of Fresh WaterDistribution of Fresh Water

IntroductionIntroduction Groundwater: water within the zone of saturation Zone of Saturation: zone where all pore spaces

are filled with water Water Table: upper limit of zone of saturation Zone of Aeration: area above water table that

includes capillary fringe, and belt of soil moisture Capillary Fringe: groundwater is held by surface

tension only Belt of Soil Moisture: zone above the water table

where water is held by molecular attraction

Groundwater: water within the zone of saturation Zone of Saturation: zone where all pore spaces

are filled with water Water Table: upper limit of zone of saturation Zone of Aeration: area above water table that

includes capillary fringe, and belt of soil moisture Capillary Fringe: groundwater is held by surface

tension only Belt of Soil Moisture: zone above the water table

where water is held by molecular attraction

Water TableWater Table

Interaction of

Groundwater with Surface Water

Interaction of

Groundwater with Surface Water Gaining

stream Losing

stream

Gaining stream

Losing stream

Characteristics of MaterialsCharacteristics of Materials

Porosity: % of total volume of rock or sediment what consists of void spaces

Permeability: ability to transmit a fluid Aquifer: layers that transmit

groundwater freely Aquitard: layers that prevent

groundwater movement

Porosity: % of total volume of rock or sediment what consists of void spaces

Permeability: ability to transmit a fluid Aquifer: layers that transmit

groundwater freely Aquitard: layers that prevent

groundwater movement

Materials & Groundwater Yield

Materials & Groundwater Yield

aquitard

aquitard

aquitard

aquiferaquifer

aquiferaquifer

Movement of GroundwaterMovement of Groundwater

Hydraulic GradientHydraulic Gradient Darcy’s Law: Q = K A (h1-h2)

d Q = discharge (m3 / s) K = hydraulic conductivity A = cross-sectional area of aquifer

Darcy’s Law: Q = K A (h1-h2) d

Q = discharge (m3 / s) K = hydraulic conductivity A = cross-sectional area of aquifer

Hydraulic gradient = slope of water table

SpringsSprings

Hot Springs & GeysersHot Springs & Geysers

WellsWells

Artesian WellsArtesian Wells

Problems Associated with Groundwater WithdrawalProblems Associated with Groundwater Withdrawal

Subsidence Saltwater Contamination Other Contamination

Septic tanks Agricultural chemicals Acid mine run-off Materials from landfills

Subsidence Saltwater Contamination Other Contamination

Septic tanks Agricultural chemicals Acid mine run-off Materials from landfills

SubsidenceSubsidence

Septic ContaminationSeptic Contamination

Geologic Work of Groundwater

Geologic Work of Groundwater

Caverns Speleothems: dripstone features found in

caverns Stalactites: on ceiling, reaching toward floor Stalagmites: on floor, reaching toward

ceiling Karst Topography

Sinkholes (AKA Sinks): depressions formed from subsidence due to underground cavers

Caverns Speleothems: dripstone features found in

caverns Stalactites: on ceiling, reaching toward floor Stalagmites: on floor, reaching toward

ceiling Karst Topography

Sinkholes (AKA Sinks): depressions formed from subsidence due to underground cavers

Caverns & SpeleothemsCaverns & Speleothems

Karst TopographyKarst Topography

SinkholesSinkholes