This document discusses various topics related to hydrogeology. It describes groundwater as a resource, explaining the properties of aquifers and how they are measured in the field. It also discusses how groundwater interacts with engineering projects and can be tapped as a resource. Finally, it covers common sources and transport of groundwater contamination.

1. Lecture
Hydrogeology
1. Water cycle
2. Groundwater Properties
3. Aquifers & Pumping tests
4. UK Aquifers
5. Hydrogeology and Construction
6. Groundwater Contamination

2. The Water Cycle
Reservoir
Average
residence time
Antarctica 20,000 years
Oceans 3,200 years
Glaciers 20 to 100 years
Seasonal snow cover 2 to 6 months
Soil moisture 1 to 2 months
Groundwater: shallow 100 to 200 years
Groundwater: deep 10,000 years
Lakes 50 to 100 years
Rivers 2 to 6 months
Atmosphere 9 days
PhysicalGeography.net
Price; Introducing Groundwater
• Describes the continuous movement
of water on, above and below the
Earth’s surface
• Water moves from one reservoir to
another:
• River to ocean
• Ocean to atmosphere
• By physical processes :
• Evaporation
• Condensation
• Precipitation
• Run-off*
• Subsurface flow*
*Of most interest to hydrogeologists and
engineering geologists

3. Earth’s Water Resources
(C) Copyright, 1996 by Purdue Research Foundation, West Lafayette, Indiana 47909, All Right
Reserved. This material may be reproduced and distributed in its entirely for non-profit, educational use,
provided appropriate copyright notice is acknowledged.
Surface/fresh water excluding ice
• 1400 M km3: Total Volume of water
• 96.5 %: saline water of oceans
• 2 %: glaciers and polar ice-caps
• 0.02 %: rivers and streams
• ~1-1.5 %: GROUNDWATER
• 7-60 M km3
• Estimates difficult due to permafrost,
seasonal ice & impermeable rocks

4. Groundwater in rocks and soils
(C) Copyright, 1996 by Purdue Research Foundation, West Lafayette, Indiana 47909, All Right Reserved. This material may be
reproduced and distributed in its entirely for non-profit, educational use, provided appropriate copyright notice is acknowledged.
• Water exists in the ground within the saturated and unsaturated
zone
• Unsaturated zone: pores/voids partially filled
• Saturated zone: pores/voids completely filled

5. Groundwater in rocks and soils
Unsaturated
Zone
Saturated
Zone
• Unsaturated zone: water held as a film around grains, water at less than
atmospheric pressure
• Capillary fringe: ~saturated water above the water table at pressure less than
atmospheric due to surface tension and capillary phenomena
• Groundwater recharged by downward flow of water due to gravity
• Saturated zone: below the water table ‘groundwater’ at a pressure above
atmospheric
‘Groundwater’

6. Groundwater in rocks and soils
• How/why does water flow in the ground?
• Differences in water table heights (elevation and pressure)
• Water works to equalize the difference by flowing
• Therefore flow occurs from high ‘head’ to low ‘head’
• Flow cells Recharge
zone
Discharge
zone
Groundwater
circulatory systems
Discharge at
rivers
Recharge during
Winter
impermeable
permeable

7. Perched water tables
(C) Copyright, 1996 by Purdue Research Foundation, West Lafayette, Indiana 47909, All Right Reserved. This material
may be reproduced and distributed in its entirely for non-profit, educational use, provided appropriate copyright notice is
acknowledged.
• Water table within low permeability lenses
• Above regional water table

8. Groundwater Properties
• At what depth is groundwater reached?
Northumberlandtoday.com
Wikipedia
Water table at 2-3 m BGL 20-200 m deep, Qanats
Alluvial fan, Iran

9. Groundwater Properties
• Term ‘groundwater’ either refers to 1) water in rocks 2) the
exploitable commodity
• Is not evenly distributed throughout the Earth’s crust;
– some lithologies concentrate groundwater and permit flow easily
through it
– others hold groundwater and only permit very slow flow rates and
small volumes
• Some areas do not get sufficient recharge
– Water not available to enter subsurface, high rates of
evapotranspiration (Evp)
• Large areas of the UK where groundwater exists but can not
be exploited as a resource
– Mainly due to properties of the lithologies in which the water exists

10. Groundwater Properties
Porosity:
• Measure of pore space
• How porous the rocks are; 𝑛 = 𝑉
𝑝 𝑉𝑏 ∙ 100 (= Volume of void
space/total rock volume)
Permeability (=hydraulic conductivity):
• A measure of the ease with which water can flow through a
rock
• Permeable materials permit water to flow through them
(impermeable contrary)
• A function of connectivity and grain size of geological material
• High porosity does not mean high permeability, an example:
Cretaceous Chalk

11. Groundwater Properties
Permeability: Flow takes place by:
• Intergranular flow – diffuse flow, between grains
in sands and gravels, poorly cemented
sandstones and young porous limestones
• Fracture flow – through joints, bedding etc;
erratic flow in faults; dense joint sets provide
diffuse flow in chalks
• Secondary flow - groundwater flow increasing
permeability by dissolution, notably in
limestones, karst systems,
• Limestones at Castleton,
• Derbyshire
Inchnadamph

12. Groundwater as a resource
• Like many natural resources, if groundwater is to
be exploited as a resource;
• It must exist in economically viable quantities
• This situation is met where:
1. Layers of rock are sufficiently porous to store water
2. Permeable enough to allow flow through
• These conditions exist: Aquifer
• Unconfined aquifer: upper surface water table
• Confined aquifer: low permeability confining
layer overlying aquifer

13. Types of Aquifers
(C) Copyright, 1996 by Purdue Research Foundation, West Lafayette, Indiana
47909, All Right Reserved. This material may be reproduced and distributed in its
entirely for non-profit, educational use, provided appropriate copyright notice is
acknowledged.
Unconfined
Aquifer
Confined
Aquifer
Groundwater must be abstracted
by pumping
Groundwater flows as
under pressure

14. Aquifer Properties
One of the most important and easiest properties:
• Hydraulic Conductivity, k, m/s:
– A measure of how much water can naturally flow
– Is dependent on the hydraulic gradient, 𝑖:
𝒊 =
𝑯
𝒍
𝒊
𝑯
• Slope of the water table
• Typical 𝑖 for an aquifer =
1:100

15. • Hydraulic Conductivity, k
– Flow rate, Q
– Area of the aquifer:
– B = aquifer thickness, m
– w = aquifer width, m
• Darcy’s Law is used to describe the flow through an
aquifer
• For a given material, K, remains constant;
proportionality constant
Aquifer Properties
𝑲 =
𝑸
𝑩𝒘𝒊
Darcy’s apparatus to experimentally
verify his concept in Dijon, 1803

16. Other Aquifer Properties
• Specific yield - % volume of water that can drain freely
from a rock; indicates the groundwater resource value
of an aquifer (some water not extractable)
• Storage Coefficient/Storativity – volume of water
released from an aquifer for each unit change of water
table height
• Transmissivity, T – hydraulic conductivity of a vertical
section of aquifer, hence: 𝑇 = 𝐾𝐵
– How readily water can move through aquifer to wells

17. Typical Aquifer Values
Material Permeability
K (m/day)
Porosity % Specific yield
%
Granite 0.0001 1 0.5
Shale 0.0001 3 1
Clay 0.0002 50 3
Fractured sandstone 5 15 8
Sand 20 30 28
Gravel 300 25 22
Cavernous limestone erratic 5 4
Chalk 20 20 4
Fracture zone (e.g. fault) 50 10
K< 0.01 m/day – impermeable K>1 m/day – exploitable aquifer

18. Field Measurement of Aquifer Properties
Regional Aquifer Properties
• Cone of depression forms in piezometric surface during abstraction
• Shape: pumping rate, transmissivity and storativity of aquifer
• Pump water out at a steady rate while monitoring the fall in water table in at
least 2 monitoring wells
• Draw down proportional to pump rate

19. Local Aquifer Properties
• Packer test used to determine individual contributions to overall aquifer
transmissivity of particular layers or fissures
• Can be either constant head or falling head
Field Measurement of Aquifer Properties

20. UK Aquifers
UK Groundwater Forum
Cretaceous Chalks
• Shell fragments
• Porosity 40 %
• Specific yield = ~1 %
• T = 1000 m2/day
• Cracks and fissures
• Bedding flow
Permo-Triassic Sandstones
• Penrith Sandstone
• Dune sands
• Intergranular flow
• Porosity 20-35 %
• K = 1-10 m/day
Most important UK aquifers occur in ‘Younger Cover’
• Annual abstraction:
2400M m3/day
• 85% from two aquifers

21. UK Aquifers
Example of a hydrogeological
map
(BGS)
Hydrochemistry &
abstraction licenses
Relief & Annual Rainfall
data
Hydrograph data
Geological cross sections
Hydrogeological Map:
• Piezometric contours
• Surface water courses
• Rainfall catchments
Stratigraphic column with
hydrogeological properties

22. UK Aquifers
Example of a hydrogeological map: close up BGS
1 km
Permian
Breccias
Flow direction
Piezometric
contours
Contours of base
Otter Sandstone aquifer
Rivers,
streams &
Sea
Rainfall
catchments
Drift material

23. Hydrogeological model
• More than one groundwater flow path exists

24. Groundwater Resources
Abstraction Well Design
• Example abstraction well
connected to three aquifers
• Borehole supported by steel
casing
• Grout between casing and rock
for sanitary reasons
• Perforated screen used for loose
sands prevents up flow of
sediment
• Gravel filter pack for fine sands
• Unlined for rocks as support not
needed

25. Resource Considerations
• Aquifer abstraction stability is only assured if the
rate of abstraction < recharge.
• If abstraction > recharge = groundwater mining
(e.g. Great Man-made River)
• Groundwater quality is ensured by:
– aquifer filtration while flowing
– underground residence time in contact with
absorptive clays and cleansing bacteria in soils

26. Tapping an aquifer…
“Eighth wonder of the world” Colonel Gaddafi
• Worlds largest water irrigation project
• Supply 70 % of overall water demand
• 6,500,000 m3 per day
• Abstract groundwater from Nubian Sandstone
Aquifer in Sahara
• Fossil aquifer; no recharge
• Potential water reserves: 150,000 km3
• Transport to cities of Tripoli, Benghazi & Sirte

27. Tapping an aquifer…
“Eighths wonder of the world” Colonel Gaddafi
• Worlds largest water irrigation project
• Supply 70 % of overall water demand
• 6,500,000 m3 per day
• Abstract groundwater from Nubian Sandstone
Aquifer in Sahara
• Fossil aquifer; no recharge
• Potential water reserves: 150,000 km3
• Transport to cities of Tripoli, Benghazi & Sirte
• 1300 abstraction wells down to 500 m
• 2820 km of pipes and aquaducts
• Several huge reservoirs

28. Groundwater & Engineering Works
• Any construction project working in the saturated
zone will be affected by groundwater
• Groundwater exclusion techniques:
Sheet Piling
Diaphragm Walling
Prweb.com Menardbachy.au

29. Groundwater & Engineering Works
• Any construction project working in the saturated
zone will be affected by groundwater
• Groundwater exclusion techniques:
Grouting
Bachysoletanche
.com

30. Groundwater & Engineering Works
• Any construction project working in the saturated
zone will be affected by groundwater
• Dewatering techniques:
• Pumping to lower
water table
• Also used in deep
mining
Moorcroft Quarry,
Plymouth
Price 2002

31. Groundwater & Engineering Works
• Any construction project working in the saturated
zone will be affected by groundwater
• Drainage:
• Remove water that
enters works
• Remove water before
it can be an issue

32. Groundwater & Engineering Works
• Any construction project working in the saturated
zone will be affected by groundwater
• Drainage:
• Reduces strength
of foundations
• Remove and
prevent water from
flowing
Pump water out
via gallery and borehole
Grout curtain

33. Groundwater Contamination
EU Water Framework Directive
• Europe’s Water protection policy
In terms of groundwater:
1. Prevent input of pollutants
2. Recharge-discharge
balance
3. Reverse current pollutant
concentration trends
4. Do all the above within 15
years

34. Groundwater Contamination
Common contaminants:
1. Petroleum products
2. Fertilizers
3. Pesticides
4. Human waste (sewerage)
5. Nitrates
Contaminant sources:
1. Storage tanks (point source)
2. Septic systems
3. Fly-tipping of waste
4. Contaminated water courses
5. Landfills
6. Roads and railways (line
source)
7. Salt water intrusion
8. Farming (diffuse source)
Contaminant Transport
Advection; with
groundwater
Diffusion & dispersion

35. Groundwater Contamination
Common contaminants:
1. Petroleum products
2. Pesticides
3. Human waste (sewerage)
4. Nitrates
Contaminant sources:
1. Storage tanks (point source)
2. Septic systems
3. Fly-tipping of waste
4. Contaminated water courses
5. Landfills
6. Roads and railways (line
source)
7. Salt water intrusion
8. Atmospheric contaminants
Contaminant Transport
Advection; with
groundwater
Diffusion & dispersion
• Herbicides, pesticides and fungicides used to kill
weeds & insects
• Soluble and susceptible to leaching; easily reach GW
• Restrictions in use near public supply wells

36. Groundwater Contamination
Common contaminants:
1. Petroleum products
2. Pesticides
3. Human waste (sewerage)
4. Fertilisers: Nitrates
Contaminant sources:
1. Storage tanks (point source)
2. Septic systems
3. Fly-tipping of waste
4. Contaminated water courses
5. Landfills
6. Roads and railways (line
source)
7. Salt water intrusion
8. Atmospheric contaminants
Contaminant Transport
Advection; with
groundwater
Diffusion & dispersion
• High concentrations detrimental to health (infants)
• Risk of groundwater contamination managed
• Designated ‘Nitrate Vulnerable Zones’
• Farmers encouraged to adapt farming practices

37. Summary
• Groundwater as a resource
• Types of aquifers
• Groundwater movement & field measurement
• Aquifer well design & aquifer exploitation example
• Hydrogeology and engineering projects
• Groundwater contamination