the water beneath our feet: understanding the groundwater...
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The Water Beneath Our Feet:
Understanding the GroundwaterResource
Kerry MacQuarrieKerry MacQuarrieDepartment of Civil Engineering Department of Civil Engineering
& Canadian Rivers Institute& Canadian Rivers Institute
University of New BrunswickUniversity of New Brunswick
Fredericton, NBFredericton, NB
In a In a 19041904 decision, Houston & Texas Central decision, Houston & Texas Central
Railway v. East, the Texas Supreme Court refused Railway v. East, the Texas Supreme Court refused
to protect adjoining landowners (from the effects of to protect adjoining landowners (from the effects of
pumping) because it thought that the principles that pumping) because it thought that the principles that
control the movement of groundwater were:control the movement of groundwater were:
""so secret, occult, and concealed that an attempt to so secret, occult, and concealed that an attempt to
administer any set of legal rules [would result] in administer any set of legal rules [would result] in
hopeless uncertainty, and would, therefore, be hopeless uncertainty, and would, therefore, be
practically impossiblepractically impossible."."
Source: R.J. Glennon, 2004, Water Follies: Groundwater Pumping and the Water Follies: Groundwater Pumping and the
Fate of AmericaFate of America’’s Fresh Waterss Fresh Waters
Presentation ContentPresentation Content
1. Some groundwater basics.
2. What are the hydrologic flow implications of groundwater extraction?
3. Groundwater and stream temperature.
4. Where are we now (it’s not 1904 and we are not in Texas!)
Groundwater
A water resource (renewable, or non-renewable?) that is:
• Widely available
• Generally of good quality
• Relatively inexpensive
In many parts of the world there is no alternative to
groundwater for meeting freshwater requirements.
The Global Hydrologic Cycle
Source: Adapted from the United Nations Environment Programme
• Globally, groundwater plays a
central role in agriculture – for
example, 70% of all
groundwater extracted in the
US is used for irrigation.
•• The natural discharge of The natural discharge of
groundwater also supports groundwater also supports
ecosystems (streams, ecosystems (streams,
wetlands, etc.).wetlands, etc.).
The Importance of Groundwater
•• Almost 10 million Canadians Almost 10 million Canadians
use groundwater for drinking use groundwater for drinking
water. water.
•• Water supply for over 80% of Water supply for over 80% of
CanadaCanada’’s rural population.s rural population.
•• Especially important in PEI.Especially important in PEI.
The Importance of Groundwater
• Aquifers are the geological “units” that
transmit and store
groundwater.
•• They can be small, They can be small,
large, shallow or large, shallow or
deep.deep.
• Residence time of
groundwater in aquifers can vary from
years to millennia.
Source: Council of Canadian Academies, 2009
base flowstream flow
=Base flow index (BFI)Base flow index (BFI)
Source: Grizard, in preparation
• Groundwater is typically cooler in summer than
surface water (and warmer in winter).
Source: Danielescu et al., 2009
Groundwater Extraction by Groundwater Extraction by
PumpingPumping
RechargeRecharge
DischargeDischarge
Pre-development
DischargeDischarge
aquiferaquifer
RechargeRecharge
((unaffectedunaffected))ExtractionExtraction
Groundwater extraction
•• Pumping wells first draw water from Pumping wells first draw water from ““storagestorage”” ––
draining water from the waterdraining water from the water--filled pores and filled pores and
fractures close to the well.fractures close to the well.
•• Then gradually begin to Then gradually begin to ““capturecapture”” groundwater groundwater
flow that would normally discharge to surface flow that would normally discharge to surface
water.water.
•• If pumping rate/duration is high/long enough, may If pumping rate/duration is high/long enough, may
reverse flow direction and induce surface water reverse flow direction and induce surface water
infiltration into the aquifer.infiltration into the aquifer.
Groundwater Extraction
Source: Barlow and Leake, 2012
•• When aquifer storage is no longer a source of When aquifer storage is no longer a source of
water to the well(s), then all of the pumped water water to the well(s), then all of the pumped water
must result in decreased stream flow must result in decreased stream flow –– either by either by
captured discharge or induced infiltration.captured discharge or induced infiltration.
•• But, it takes time for full stream depletion to occur But, it takes time for full stream depletion to occur
(and it takes time to (and it takes time to ““recoverrecover”” after pumping after pumping
stops).stops).
•• Distance of well(s) from stream, aquifer Distance of well(s) from stream, aquifer
parameters, pumping pattern, all play a role.parameters, pumping pattern, all play a role.
Groundwater Extraction
Groundwater Extraction
350 m350 m
hypotheticalhypothetical
wellwell
• Assumed some “typical” PEI aquifer hydraulic parameter values (need to know these values to make calculations).
•• Cumulative impact of Cumulative impact of
multiple pumping wells can multiple pumping wells can
be significant (and so must be significant (and so must
be assessed/managed).be assessed/managed).
•• Consider the history of Consider the history of
irrigation in western irrigation in western
Kansas (semiarid climate; Kansas (semiarid climate;
but overlies one of the but overlies one of the
major aquifers in North major aquifers in North
America).America).
Groundwater Extraction
Source: Sophocleous, 2012
History of groundwater allocation and rights in Kansas
Groundwater and Stream Water Groundwater and Stream Water
TemperatureTemperature
•• Annual groundwater temperature fluctuations Annual groundwater temperature fluctuations
are relatively small, so groundwater discharge are relatively small, so groundwater discharge
provides a stable temperature environment for provides a stable temperature environment for
fish and other aquatic organisms.fish and other aquatic organisms.
Groundwater Temperature
Source: Bartlett, 2011
•• If the groundwater discharge is localized, then it If the groundwater discharge is localized, then it
may also create may also create ““thermal refugethermal refuge”” for fish species for fish species
during warm water events.during warm water events.
•• Example from a New Brunswick river:Example from a New Brunswick river:
Source: Wilbur, 2012
Flow
Source: Barlow and Leake, 2012
Groundwater Temperature
•• Groundwater pumping may cause stream Groundwater pumping may cause stream
temperatures to increase during the summer, temperatures to increase during the summer,
but there is a lack of empirical evidence to but there is a lack of empirical evidence to
determine the magnitude of such increases.determine the magnitude of such increases.
•• Data from a small stream (Otter Brook) in central Data from a small stream (Otter Brook) in central
New Brunswick:New Brunswick:
Confluence
East Branch
West Branch
Source: Somers, 2013
June 2010June 2010
Source: Somers, 2013
•• Effect of a hypothetical reduction in base flow of Effect of a hypothetical reduction in base flow of
½½, applied to each base flow location (reduced , applied to each base flow location (reduced
total groundwater discharge to brook by about total groundwater discharge to brook by about
0.075 m0.075 m33/sec or 1000 igpm)./sec or 1000 igpm).
Source: Somers, 2013
SummarySummary
•• The hydrologic understanding and methods used The hydrologic understanding and methods used
to evaluate groundwaterto evaluate groundwater--stream interactions have stream interactions have
progressed significantly in the past 10 to 20 years.progressed significantly in the past 10 to 20 years.
•• The extraction of groundwater should be expected The extraction of groundwater should be expected
to have some impact on surface water; the to have some impact on surface water; the
magnitude of the impact will depend on the nature magnitude of the impact will depend on the nature
of the pumping and the aquifer/stream properties.of the pumping and the aquifer/stream properties.
•• With information (data), there are tools than With information (data), there are tools than
enable forecasts to be made. enable forecasts to be made.
Summary
Source: Council of Canadian Academies, 2009
Sustainability Goals for Groundwater
Source: Council of Canadian Academies, 2009
““An aquifer is like a milkshake An aquifer is like a milkshake
glass and each well is the glass and each well is the
equivalent of a straw in the equivalent of a straw in the
glass. What most countries glass. What most countries
permit is a limitless number of permit is a limitless number of
straws in the glass. This is a straws in the glass. This is a
recipe for disaster.recipe for disaster.””
R. Glennon, University of Arizona, 2012R. Glennon, University of Arizona, 2012
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