INTRODUCTION
 HYDROLOGY and HYDROGEOLOGY
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Scope of Hydrogeology
Historical Developments in Hydrogeology
Hydrologic Cycle
groundwater component in hydrologic cycle,
Hydrologic Equation
 HYDROLOGY and HYDROGEOLOGY
 HYDROLOGY:
 the study of water. Hydrology addresses the occurrence, distribution,
movement, and chemistry of ALL waters of the earth.
 HYDROGEOLOGY: includes the study of the interrelationship of
geologic materials and processes with water,
 origin
 Movement
 development and management
• Geologic materials
• Rocks
• Minerals
• Processes
• Mechanical processes
• Chemical processes
• Thermal processes
• More comprehensive definition:
it is "the study of the laws governing the movement of subterranean
water, the mechanical, chemical, and thermal interaction of this
water with the porous solid, and the transport of energy and
chemical constituents by the flow".
Hydrogeology
• Descriptive science
• Analytic and
Quantitative
science
• Why
hydrogeology?
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Exploration
Development
Inventory
Management
Scope Of Hydrogeology
A. Physical Hydrogeology
1.
2.
3.
4.
Exploration:
Development:
Inventory:
Management:
B. Chemical hydrogeology
1.
2.
3.
chemistry and transport of contaminants
chemical characteristics of groundwater
chemical evolution along flow paths
C. Groundwater in eng. applications and other earth
sciences:
subsidence, sinkholes, earthquakes, mineral deposits etc.
D. Mathematical Hydrogeology:
an approximation of our understanding of the physical system
THE BUSINESS OF
HYDROGEOLOGY
• Groundwater Supply and Control
1.Design test wells
2.Construct productive wells
3.Develop regional sources of groundwater
4.Review cost estimates
5.Determine water quality
6.Involve in aquifer protection and water
conservation
7.Designing dewatering wells for construction
and mining projects
• Solution of Groundwater
Contamination Problems
1.Remediate contaminated aquifers
2.Design Groundwater monitoring and quality
plans
3.Analyze collected groundwater samples
4.Propose waste disposal sites for:
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Petrochemical plants
Mining industries
Municipal wastes
Gasoline storage tanks
• Research and Academy
1.Develop new methods and techniques
2.Solve hydrologic and contamination
problems
3.Help developing new equipment
• Geophysical devices
• Sampling apparatus
4.Develop computer programs to solve
hydrogeologic problems
• Pumping test software
• Numerical simulators
• Hydrogeologic mapping programs
HISTORICAL DEVELOPMENT OF
HYDROGEOLOGY
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Old nations
Chines
Egyptians
Romans
Persians
Arabs
Central
trough
Portgarl and
wheel
Shaft to prime
mover
Mountain
Mother well
Qanat
End of qanat
Water producing
section
Impermeable rock
Alluvium
Water table
Islamic Civilization
• Canals and water ways
• Storage ponds
• Mathematics and geometry
• Physical sciences
Nineteenth Century
• 1856 Darcy’s law
• 1885 Water flow under artesian
conditions
• 1899 Flow of groundwater & field
observations
Twentieth Century
• 1923 Groundwater in USA
• 1928 Mechanics of porous media
• 1935 Solution of transient behavior
of water
• 1940 Development of governing flow
equations
• 1942 Well hydraulics fundamentals
• 1956 Chemical character of natural
water
• 1960 Regional geochemical
processes
• 1970 Geothermal energy
resources
• 1975 Environmental issues
• 1980 Contaminant transport
• 1985 Stochastic techniques
• 1990’s modeling and management
issues
Hydrologic Cycle
• Saline water in oceans accounts for 97.2% of total water on
earth.
 Land areas hold 2.8% of which ice caps and glaciers hold
76.4% (2.14% of total water)
 Groundwater to a depth 4000 m: 0.61%
 Soil moisture .005%
 Fresh-water lakes .009%
 Rivers 0.0001%.
 >98% of available fresh water is groundwater.
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Hydrologic CYCLE has no beginning and no end
Water evaporates from surface of the ocean, land, plants..
Amount of evaporated water varies, greatest near the equator.
Evaporated water is pure (salts are left behind).
 When atmospheric conditions are suitable, water vapor
condenses and forms droplets.
 These droplets may fall to the sea, or unto land (precipitation)
or may evaporate while still aloft
 Precipitation falling on land surface enters into a
number of different pathways of the hydrologic
cycle:
 some temporarily stored on land surface as ice and
snow or water puddles (depression storage)
 some will drain across land to a stream channel
(overland flow).
 If surface soil is porous, some water will seep into the
ground by a process called infiltration (ultimate
source of recharge to groundwater).
 Below land surface soil pores contain both air and
water: region is called vadose zone or zone of
aeration
 Water stored in vadose zone is called soil moisture
 Soil moisture is drawn into rootlets of growing plants
 Water is transpired from plants as vapor to the
atmosphere
 Under certain conditions, water can flow laterally in
the vadose zone (interflow)
 Water vapor in vadose zone can also migrate to land
surface, then evaporates
 Excess soil moisture is pulled downward by gravity
(gravity drainage)
 At some depth, pores of rock are saturated with
water marking the top of the saturated zone.
 Top of saturated zone is called the water table.
 Water stored in the saturated zone is known as ground
water (groundwater)
 Groundwater moves through rock and soil layers until it
discharges as springs, or seeps into ponds, lakes,
stream, rivers, ocean
 Groundwater contribution to a stream is called baseflow
 Total flow in a stream is runoff
 Water stored on the surface of the earth in ponds, lakes,
rivers is called surface water
• Precipitation intercepted by plant leaves can evaporate
to atmosphere
Groundwater component
in the hydrologic cycle
• Vadose zone = unsaturated zone
• Phreatic zone = saturated zone
• Intermediate zone separates phreatic
zone from soil water
• Water table marks bottom of capillary
water and beginning of saturated zone
Distribution of Water in the Subsurface
Units are relative to annual P on land surface
100 = 119,000 km3/yr)
Hydrologic Equation
• Hydrologic cycle is a network of inflows and outflows,
expressed as
• Input - Output = Change in Storage
(1)
• Eq. (1) is a conservation statement: ALL water is
accounted for, i.e., we can neither gain nor lose water.
• On a global scale
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–
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–
–
–
atmosphere gains moisture from oceans and land areas E
releases it back in the form of precipitation P.
P is disposed of by evaporation to the atmosphere E,
overland flow to the channel network of streams Qo,
Infiltration through the soil F.
Water in the soil is subject to transpiration T, outflow to the
channel network Qo, and recharge to the groundwater RN.
• The groundwater reservoir may receive
water Qi and release water Qo to the
channel network of streams and
atmosphere.
• Streams receiving water from
groundwater aquifers by base flow are
termed effluent or gaining streams.
• Streams losing water to groundwater
are called influent or losing streams
• A basin scale hydrologic subsystem is
connected to the global scale through P, Ro
, equation (1) may be reformulated as
P - E - T -Ro = DS (2)
DS is the lumped change in all subsurface
water. All terms have the unit of discharge,
or volume per unit time.
• Equation (2) may be expanded or
abbreviated depending on what part of the
cycle we are interested in. for example, for
groundwater component, equation (2) may
be written as
RN + Qi - T -Qo = DS
(3)
• Over long periods of time, provided basin is
in its natural state and no groundwater
pumping taking place, RN and Qi are
balanced by T and Qo, so change in storage
is zero. This gives:
RN + Qi = T + Q0
(4)
• => groundwater is hydrologically in a
steady state.
• If pumping included, equation (4) becomes
RN + Qi - T -Qo - Qp = DS
(5)
Qp= added withdrawal.
• As pumping is a new output from the
system,
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water level will decline
Stream will be converted to a totally effluent,
transpiration will decline and approach zero.
Potential recharge (which was formerly rejected due
to a wt at or near gl) will increase.
– Therefore, at some time after pumping starts,
equation (5) becomes:
RN + Qi - Qo - Qp = DS (6)
• A new steady state can be achieved if
pumping does not exceed RN and Qi.
• If pumping exceeds these values, water is
continually removed from storage and wl
will continue to fall over time. Here, the
steady state has been replaced by a
transient or unsteady state.
• In addition to groundwater being depleted
from storage, surface flow has been lost
from the stream.
Example
groundwater changes in
response to pumping
Inflows
ft3/s Outflows
ft3/s
1. Precipitation
2475
2. E of P
1175
3. gw discharge to sea
725
4. Streamflow to sea
525
5. ET of gw
25
6. Spring flow
25
Example, contd.
• Write an equation to describe water balance.
SOLUTION:
Water balance equation:
Water input from precipitation – evapotranspiration of
precipitation – evapotranspiration of groundwater –
stream flow discharging to the sea – groundwater
discharging to the sea – spring flow = change in storage
P –ETp – ETgw –Qswo – Qgwo –Qso = ∆S
Example, contd
• Is the system in steady state?
Substitute appropriate values in above
equation:
2475 – 1175 -25 -525 -25 = ∆S =0