Groundwater Systems

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Groundwater Systems

• Ian Clark
• 26 April 2006

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Reference

• Text Chapter 13

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Introduction

• Groundwater systems
• Water Table and Aquifers
• Movement of Groundwater
• Natural Artificial Discharge
• Groundwater Resources

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Groundwater Systems

• The hydrological cycle
• Groundwater
• Recharge Discharge
• Porosity Permeability

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Major Idea

• Groundwater is an integral part of the
  hydrological system and is intimately related to
  surface water drainage

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Hydrological Cycle
Condensation
Rain clouds
Transpiration from plants
Transpiration
Precipitation
Precipitation
Evaporation
Precipitation to ocean
Evaporation From ocean
Infiltration and percolation
Surface runoff (rapid)
Groundwater movement (slow)
Ocean storage
Groundwater movement (slow)
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Groundwater

• Groundwater is water contained below the surface
  in rocks and soils
• Moves under the influence of gravity
• Enters from the surface as water percolates
  downwards (recharge)
• Leaves the system by seeping into rivers,
  streams, lakes and springs (discharge)
• Can travel long distances

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GreatArtesianBasin
http//www.nrm.qld.gov.au/water/gab/images/map.GIF
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Porosity and Permeability

• Major Idea
• Rock porosity and permeability control flow and
  movement

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Porosity Permeability

• Control the storage and passage of groundwater
• Porosity is of void space in a rock, sediment
  or soil
• Permeability refers to the ability of material to
  transmit fluids

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Porosity

• of void space
• Voids may be
• Spaces between grains
• Fractures
• Solution cavities
• vesicles

http//www.earthsci.org/mineral/rockmin/sed/pores.
gif
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Permeability

• Varies with rock type
• High sandstone, conglomerate, limestone, basalt
• Low shale, unfractured crystalline rocks,
  highly cemented sedimentary rocks
• Flow rate -1m/day to 1m/yr

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Water Table and Aquifers

• Major Idea
• The water table is the top of the saturated zone

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Water Table

• Level to which water will rise in a well
• Top of the saturated zone

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Water table
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Aquifers aquicludes

• Major Idea
• Aquifers are saturated permeable rocks and may be
  perched, confined or unconfined

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Aquifers aquicludes

• Aquifer is a permeable zone or formation that is
  saturated with water
• Aquiclude is an impermeable zone or formation
• Unconfined aquifer is connected to the surface by
  open pore spaces through which it can be
  recharged
• Confined aquifer is enclosed between impermeable
  strata
• Perched aquifer is a lens of porous water
  saturated rock that is above the regional water
  table

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Aquifers
Confined aquifer
Unconfined aquifer
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Discharge

• Major Idea
• Natural discharge occurs in springs, streams,
  wetlands and lakes

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Discharge of Groundwater

• Natural discharge occurs where the water table
  intersects the land surface
• Springs, wetlands, stream channels or lakes

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Springs
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Fault Spring
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Wells and Bores

• Water rises to the level of the water table
• Artesian aquifer is confined and projected
  water table is above the land surface
• Sub-artesian water table is below land surface,
  aquifer may be confined or unconfined.

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Artesian sub artesian water
Sub-artesian well
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Groundwater Resources
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Ground water Resources
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Cone of depression
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Aquifer Storage Recovery(ASR)
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Alteration of Groundwater

• Major Idea
• Groundwater resources can be affected by human
  activities
• Changes in composition
• Saltwater Encroachment
• Changes in position of the water table
• Subsidence

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Contamination
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Contamination
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Saltwater encroachment
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Subsidence
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Summary

• Groundwater is an integral part of the
  hydrological system and is intimately related to
  surface water drainage
• Rock porosity and permeability control flow and
  movement
• The water table is the top of the saturated zone
• Natural discharge occurs in springs, streams,
  wetlands and lakes
• Aquifers are saturated permeable rocks and may be
  perched, confined or unconfined
• Groundwater resources can be affected by human
  activities