Monitoring groundwater and soil moisture with

observation wells

Garth van der KampWater Science and Technology, Environment Canada

Bruce Davison

John Fahlman

Kei Lo

Saul Marin

Alan Pietroniro

Craig Smith

Randy Schmidt

Brenda Toth

César Pérez Valdivia

Overview of the Geological Weighing Lysimeter

Fundamentals

Changes of mechanical surface loading are instantaneously

transmitted to deep saturated formations resulting in change of

pore water pressure;

Observation wells in confined aquifers can therefore detect pore

pressure changes due to hydrological processes such as:

Snow accumulation;

Rainfall;

Evapotranspiration

Conceptual Sketch of Geological

Weighing

Lysimeter Installation

Pressure Transducer--

t

p

tens of meters

Duck Lake observation

well site - climate

station installed in 2008.

August 2010

Spring 2001

Duck Lake SK Observation wells: water levels, 1964-2006[Source: SK Watershed Authority, www.swa.ca]

Duck Lake #1 Duck Lake #2

Aquifer

Aquitard

Aquitard

Aquifer

34 m

118 m

134 m

478

479

480

Jan-6

4

Jan-6

6

Jan-6

8

Jan-7

0

Jan-7

2

Jan-7

4

Jan-7

6

Jan-7

8

Jan-8

0

Jan-8

2

Jan-8

4

Jan-8

6

Jan-8

8

Jan-9

0

Jan-9

2

Jan-9

4

Jan-9

6

Jan-9

8

Jan-0

0

Jan-0

2

Jan-0

4

Jan-0

6

Jan-0

8

Wa

ter

lev

el (m

as

l)

Duck Lake #2 Observation well

0.000

1.000

2.000

3.000

4.000

Ja

n-6

4

Ja

n-6

6

Ja

n-6

8

Ja

n-7

0

Ja

n-7

2

Ja

n-7

4

Ja

n-7

6

Ja

n-7

8

Ja

n-8

0

Ja

n-8

2

Ja

n-8

4

Ja

n-8

6

Ja

n-8

8

Ja

n-9

0

Ja

n-9

2

Ja

n-9

4

Ja

n-9

6

Ja

n-9

8

Ja

n-0

0

Ja

n-0

2

Ja

n-0

4

Ja

n-0

6

Ja

n-0

8

Wa

ter

tab

le d

ep

th (

m) Duck Lake 1 Depth below ground level (m)

479.200

479.300

479.400

479.500

1-Jan 31-Jan 3-Mar 2-Apr 3-May 2-Jun 3-Jul 2-Aug

Wa

ter

lev

el

[m a

sl]

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Ba

rom

etr

ic p

res

su

re [

m o

f w

ate

r]

DuckL.#2 Water level Barometer

Duck Lake # 2 observation well and barometric pressure

Raw data Jan 1 – August 10, 2009

479.200

479.300

479.400

479.500

1-Jan 31-Jan 3-Mar 2-Apr 3-May 2-Jun 3-Jul 2-Aug

Wa

ter

lev

el

[m a

sl]

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Ba

rom

etr

ic p

res

su

re [

m o

f w

ate

r]

DuckL.#2 Water level DuckL.#2 corr baro DuckL.#2 corr baro+tidal Barometer

Duck Lake # 2 observation well, and barometric pressure

Raw data Jan 1 – August 10, 2009, plus corrections for barometric

(multiplied by loading efficiency of 0.798) and earth tides

479.240

479.340

1-May 31-May 1-Jul 31-Jul

Wa

ter

lev

el

[m a

sl]

DuckL.#2 Water level DuckL.#2 corr baro+tidal

Duck Lake # 2 observation well: raw data and corrected data:

Zoom in: May 1 – July 31, 2009

Duck Lake # 2 observation well raw data and corrected data, plus

Geonor accumulating rain gauge

Zoom in: June 16-June 26, 2009

479.200

479.300

16-Jun 26-Jun

Date, 2009

Wa

ter

lev

el

[m a

sl]

DuckL.#2 water level

DuckL.#2 corr baro+tidal

Geonor

0

5

10

15

20

25

30

35

40

1 2 3 4 5 6 7 8 13 14 15 16 17 18 19 19a 20 21 22

Event

Pre

cip

itati

on

(m

m)

Duck Lake No. 2 observation well

Geonor precipitation gauge

Comparison of rain event determinations:

Duck Lake #2 water level records (multiplied by 1/loading efficiency,

1/.798 = 1.26) versus Geonor gauge records

Modeling of the total moisture balanceComparison of Duck Lake No. 2 (geological weighing lysimeter) water

level record with Watflood simulation of the vertical water balance.

[Marin et al., 2010, J of Hydrology]

-400

-300

-200

-100

0

100

200

300

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

Year

Wate

r S

tora

ge C

hange (

mm

)

Vertical Water Balance - Modeled with WATFLOOD

Water level Duck Lake No. 2 - Observed

-1.000

-0.800

-0.600

-0.400

-0.200

0.000

0.200

0.400

0.600

0.800

1.000

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

Year

Wat

er le

vel c

han

ge

(m)

Duck Lake #2

Hearts Hill

Lilac

Tyner

Obs well average change (m)

Geological weighing lysimeter wells – southern Saskatchewan, 1965 - 2008

Shallow observation wells in SK – water level changes 1964-2007Water-table drawdown during the 2001-2003 drought averaged about 0.5 m,

corresponding to ~ 150 mm groundwater storage depletion

-2.500

-2.000

-1.500

-1.000

-0.500

0.000

0.500

1.000

1.500

2.000

2.500

Jan-

60

Jan-

65

Jan-

70

Jan-

75

Jan-

80

Jan-

85

Jan-

90

Jan-

95

Jan-

00

Jan-

05

Jan-

10

Years

Wa

tere

lev

el c

ha

ng

e (

m)

ATTON's Lk

CONQ 501

DUCKLAKE 1

FORGET

MELFORT

SIMPSON 13

STENEN

SWANSON

VERLO

Average

Regional water storage changes in southern Saskatchewan, 1998 - 2008:

- Average of 4 Geological Weighing Lysimeter wells,

- Average of 9 water table wells in sand aquifers (assuming specific yield = 0.30).

-0.300

-0.200

-0.100

0.000

0.100

0.200

0.300

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Years

Wat

er s

tora

ge c

hang

e (m

)

Average - Geological weighing lysimeter wells (m)

Average - shallow water table wells (m)

Summary

Observation well records can provide a useful record of regional long-

term moisture conditions:

a) Observation wells in water-table aquifers can provide a semi-

quantitative indication of moisture below the shallow soil zone

b) Geological weighing lysimeters (observation wells in deep confined

aquifers) can provide a record of total moisture balance averaged

over areas of km2.

However: The water-level records for deep confined aquifers are

commonly disturbed by the effects of pumping. Observation wells

that can serve as geological weighing lysimeters are few and far

between.

Therefore: The principal use of Geological Weighing Lysimeters may

be in validating other moisture observations and models at

selected locations, where hydrogeological conditions and surface

conditions are suitable.

References

Marin, S., G. van der Kamp, A. Pietroniro, B. Davison and B. Toth, 2010. Use of geological

weighing lysimeters to calibrate a distributed hydrological model for the simulation of land-

atmosphere moisture exchange, J of Hydrology, 383, 179-185.

Sophocleous, M., Bardsley, W.E., Healey, J., 2006. A rainfall loading response recorded at

300 m depth: Implications for geological weighing lysimeters. Journal of Hydrology 319,

237–244.

Bardsley, W.E., Campbell, D.I., 2006. An expression for land surface water storage

monitoring using a two-formation geological weighing lysimeter. Journal of Hydrology 335,

240-246.

Barr, A.G., G. van der Kamp, R.Schmidt,and T.A. Black, 2000. Monitoring the moisture

balance of a boreal aspen forest using a deep groundwater piezometer. Journal of

Agriculture and Forest Meteorology, 102, 13-24.

van der Kamp, G. and R. Schmidt, 1997. Monitoring of total soil moisture on a scale of

hectares using groundwater piezometers. Geoph. Res. Lett., 24, No.6, 719-722.

Bardsley, W.E., Campbell, D.I., 1993. A new method for measuring near-surface moisture

budgets in hydrological systems. Journal of Hydrology 154, 245–254.

van der Kamp, G., and H. Maathuis, 1991. Annual fluctuations of groundwater levels due

to loading by surface moisture. Journal of Hydrology 127, 137-152

Thank you.

Questions ?

Acknowledgements:

Saskatchewan Watershed Authority

Drought Research Initiative

Water storage changes observed for Duck Lake SK

observation wells 1965-2007:

Duck Lake No. 1 – Shallow water table well with specific yield = 0.30

Duck Lake No. 2 – Deep well in confined aquifer (geological weighing

lysimeter)

Duck Lake No. 1

Duck Lake No. 2

-400

-300

-200

-100

0

100

200

300

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Years

Wa

ter

sto

rag

e c

ha

ng

e [

mm

]

Watflood Lower zone storage (LZS)

Water Table Storage Change - Duck Lake No. 1

Observed

Comparison of Duck Lake No. 1 (water table storage change) with Watflood simulation

of the changes of groundwater storage. See comment on previous slide. More rigorous

modeling with MEC-MESH, which includes CLASS is underway.

-0.500

-0.400

-0.300

-0.200

-0.100

0.000

0.100

0.200

0.300

0.400

0.500

0.600

1998 1999 2000 2000 2002 2003 2004 2005 2006 2007 2008 2009 2010

Years

Mo

istu

re C

han

ge

(m)

Duck Lake #2

Hearts Hill

Lilac

Tyner

Obs well average change (m)

GRACE (m)

GRACE and Average of Saskatchewan Geological Weighing Lysimeter wells

Regional water storage changes in southern Saskatchewan:

- GRACE for southern Saskatchewan [provided by Yirdaw and Snelgrove]

- Average of Geological Weighing Lysimeter wells

- Average of water table wells

-0.300

-0.200

-0.100

0.000

0.100

0.200

0.300

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Years

Wat

er s

tora

ge c

hang

e (m

)

Average - Geological weighing lysimeter wells (m)

GRACE (m)

Average - shallow water table wells (m)