Groundwater

Groundwater

Infiltration
Surface materials
Topography
Vegetation
Precipitation
Groundwater Distribution
Zone of Aeration (unsaturated zone)
Capillary Fringe
Zone of saturation
Water Table
Availability of Groundwater
Porosity
Permeability
Groundwater Flow
Hydraulic conductivity
Hydraulic gradient
Discharge

Groundwater
IV. Groundwater Flow:
A. Flow Rate dependent on:
1. Speeds:
Depends on material, porosity and hydraulic conductivity
B. Discharge: water table intersects the surface = streams, lakes, swamps, springs (confined)

Groundwater

Groundwater
V. Aquifers
 Permeable body or rock/sediment that transmits and stores groundwater
 Best aquifer: unconsolidated sand and gravel or
 Well-sorted, poorly cemented sandstones or
 Highly fractured limestones and basalts
A.Unconfined Aquifer
Impermeable layer only below permeable material

Groundwater
V. Aquifers
A.
Unconfined Aquifer
Impermeable layer only below

Groundwater
V. Aquifers
B. Confined Aquifer
Impermeable layers above and below the aquifer
Often a deeper confined aquifer below an unconfined aquifer with an impermeable layer between the two
Water may flow hundreds of miles below ground
Below deserts in Nevada, eastern Utah, southern
Arizona

Groundwater
V. Aquifers
C. Artesian Aquifer
Water will gush out of a confined aquifer when well is drilled
Occurs where the confined aquifer is tilted at an angle to the Earth’s surface
Recharge location is higher than well location, pressure from behind combats gravity
City water supplier use the same idea —tall water town on Craig’s Hill

Groundwater
V. Aquifers
C. Artesian Aquifer
Water will gush out of a confined aquifer when well is drilled
Occurs where the confined aquifer is tilted at an angle to the Earth’s surface
Recharge location is higher than well location, pressure from behind combats gravity
City water supplier use the same idea tall water town on Craig’s
Hill

Groundwater
VI. Natural Springs and Geysers
A. Natural Springs : water flows freely from the ground
 Water table intersects the surface
 Water table reaches an impermeable layer
 May be hot if the groundwater is near magma or if it circulates deep enough

Groundwater
VI. Natural Springs and Geysers
B. Geysers : intermittent emission of hot water
Water descends through fractured rock
Warmed by underlying heat source
Forced up by steam under great pressure that is heated above boiling point due to overlying pressure
Water expands
Pressure is less  flashes to steam
Yellowstone: hot spot (magma)
Iceland: divergent plate boundary

Groundwater
VI. Natural Springs and Geysers
B. Geysers : intermittent emission of hot water

Groundwater
VII. Threats to groundwater
Groundwater can’t meet cities’ need
If withdrawal > recharge  regional lowering of the water table
Cone of depression
Aquifer is compressed  land subsidence
Las Vegas  3 feet
New Orleans  7 feet
Mexico City  23 feet
Central California  26 feet
(San Joaquin Valley)

VII. Threats to groundwater
Groundwater can’t meet cities’ need
If withdrawal > recharge  regional lowering of the water table

VII. Threats to groundwater
Groundwater can’t meet cities’ need
If withdrawal > recharge  regional lowering of the water table

VII. Threats to groundwater

Groundwater
VII. Threats to groundwater

VII. Threats to groundwater
Groundwater can’t meet cities’ need
If withdrawal > recharge  regional lowering of the water table
Aquifer is compressed  land subsidence
Venice >10 feet in 1500 years  flooded (lost bottom story)
Houston ~3-7 feet since 1906  problems with ocean flooding
Saltwater intrusion into aquifer
Brooklyn, NY in 1930’s turned into saltwater - now they have to ship the water in = very high cost of water

VII. Threats to groundwater
Venice >10 feet in 1500 years  flooded (lost bottom story)
Second century stone walkway beneath Venice, Italy.
Ground subsidence and rise in sea level resulted in a 13 cm rise in relative sea level/century.
Over the past century, the rise in relative sea level has reached a historical peak at 23 cm, in part due to an ill-planned industrial complex that pumped water from beneath the city from 1930 to 1970 and accelerated ground subsidence.

VII. Threats to groundwater
Cone of depression

Groundwater
VII. Threats to groundwater
Cone of depression

Groundwater
VII. Threats to groundwater
Desalinization Plant