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