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Groundwater Nitrate Distributions and Denitrification in a Portion of the Abbotsford-Sumas Aquifer, Northwest Washington
Robert Mitchell, Leslie McKee & Scott Babcock
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Abbotsford-Sumas Aquifer
The aquifer covers approximately 200 km2 and serves as a water supply for approximately 110,000 people in BC and WA.
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∆ N S
BC WA
15 - 25 m
1 - 10 m
Sumas Outwash
Glacial Marine Drift
Abbotsford-Sumas Aquifer
The aquifer is unconfined and comprised of glacial outwash sands and gravels (Sumas Outwash) deposited about 10,000 years ago.
The groundwater flows from north to south in the aquifer at an rate of about 1 to 5 meters per day (Cox and Kahle, 1999).
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Frasier and Nooksack Lowlands
Land use on the aquifer is dominated by agriculture because the surface soils are productive
The lowlands over the aquifer are agriculturally productive
Abbotsford
Sumas
Lynden
BC, Canada
Whatcom County, WA
Study area
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Frasier and Nooksack Lowlands
Land use on the aquifer is dominated by agriculture because the surface soils are productive
Whatcom County’s Raspberry Industry is # 1 in the Nation
Abbotsford
Sumas
Lynden
BC, Canada
Whatcom County, WA
Whatcom County’s Dairy Industry is # 2 in the State (~60,000 cows)
Study area
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Frasier and Nooksack Lowlands
Land use on the aquifer is dominated by agriculture because the surface soils are productive
Southern British Columbia is dominated by Raspberry and Poultry Industries
Abbotsford
Sumas
Lynden
BC, Canada
Whatcom County, WA
Study area
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N S
∆
BC, Canada Whatcom County, WA
Problem
Elevated nitrate concentrations (> 10 mg N/L) occur in the aquifer due to
shallow water table
heavy rain
agricultural land use
permeable soils
BC WA
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Our Objectives at
• Quantify nitrate concentrations and distributions in a study site adjacent to the International border.
• Attempt to distinguish BC nitrate sources from sources in Washington.
Monitor groundwater quality using shallow and deep domestic wells.
Measure nitrogen isotope values as a means to identify nitrogen sources.
Monitor surface-water quality in perennial streams.
Funding provided by the Washington State Department of Ecology (Centennial Clean Water Fund).
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Study Area
~ 6 sq miles
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PANGBORN RD
HALVERSTIC RD
VAN
BU
REN
RD
HALVERSTIC RD
Judson Lake
Pangbor Lake
JN5
JN4JN3JN2
JN1
PB5
PB4PB3
PB2PB1
V9
T1P3
V6V5
V4
V1
H8H6H5H2
H1
V10
K1
V8
V7
V3
V2T2
P2
H7H4H3
V12
BC3BC6
BC5BC4
±0 0.5 1 1.50.25
Miles
0 0.7 1.4 2.10.35Kilometers
Legend
Deep Wells
Shallow Wells
Stream Sampling Sites
Streams
CANADA
UNITE STATES
Study Area
26 wells
10 surface-water sites
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Domestic wells were sampled monthly for 2 years
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Surface Water was Sampled Bi-Monthly for 2 years
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Nitrogen Isotopes were measured quarterly for 2 years
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Water Quality Parameters were measured at the Institute for Watershed Studies Water-Quality Lab
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Nitrogen Isotopes were measured at the Colorado Plateau Stable Isotope Laboratory, Northern Arizona University
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Numerous factors may influence a nitrate concentration measured at well, including:
nitrate originating in BC
vadose zone thickness and residence time
well depth below the water table
up-gradient nutrient loading (timings and types)
seasonal precipitation and irrigation
vertical and lateral mixing due to intermingling plumes
mixing due to excessive well pumping
nitrate recirculation due to irrigation, and
denitrification (especially due to peat deposits in the area).
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Judson Lake
Pangbor Lake
V9
T1
P3
V6V5
V4
V1
H8H6H5H2
H1
V10
K1
V8
V7
V3
V2T2
P2
H7H4H3
V12
V11
BC3BC6
BC5BC4
PANGBORN RD
HALVERSTIC RD
VAN
BU
RE
N R
D
HALVERSTIC RD
±0 0.5 1 1.50.25
Miles
0 0.7 1.4 2.10.35Kilometers
Legend
3
3 - 10
10 - 15
15 - 20
20
Shallo Wells
Deep Wells
Rasp
blueberry
corn
grass
nuts
pasture
Crop Typ (2003)Nitrate m N/L
CANADA
UNITE STATES
Nitrate Results (7/02 to 6/04)
21 out of 26 wells had median nitrate values > 3 mg-N/L
14 out of 26 wells had median nitrate values > 10 mg-N/L (> EPA MCL)
Shallow wells had higher values then deeper wells, highest value was 43 mg-N/L
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H1
H2
H3
H4
H5
H6
H7
H8 K1 P1 P2 P3 T1 T2 V1 V
10V
11V
12 V2 V3 V4 V5 V6 V7 V8 V9
0
10
20
30
40N
itrat
e+N
itrite
(mgN
/L)
EPA MCL (10 mgN/L)
shallow wellsdeep wells (> 25 ft)
(< 25 ft)
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0 10 20 30 40
010
2030
40
Total Nitrogen (mgN/L)
Nitr
ate+
Nitr
ite (m
gN/L
)
tau = 0.95pvalue <2.2e16
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Judson Lake
Pangbor Lake
V9
T1
P3
V6V5
V4
V1
H8H6H5H2
H1
V10
K1
V8
V7
V3
V2T2
P2
H7H4H3
V12
V11
BC3BC6
BC5BC4
PANGBORN RD
HALVERSTIC RD
VAN
BU
RE
N R
D
HALVERSTIC RD
±0 0.5 1 1.50.25
Miles
0 0.7 1.4 2.10.35Kilometers
Legend
3
3 - 10
10 - 15
15 - 20
20
Shallo Wells
Deep Wells
Rasp
blueberry
corn
grass
nuts
pasture
Crop Typ (2003)Nitrate m N/L
CANADA
UNITE STATES
Nitrate Results (7/02 to 6/04)
Nitrate concentrationswere higher in wells north of PangbornLake and Creek
12 out of 15 wells had median nitrate values > 10 mg-N/L
Lower values at V7, V10 and V12 are likely due to denitrification.
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•Judson Lake
Study Area
Pangborn Bog
BCWA
H-3
V-9
H-4
V-8
Wells near the border are likely receivinggroundwater and (nitrate) from BC
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Deep Wells Near the Border
0
5
10
15
20
25
30
35
Mar-02 May-02 Aug-02 Nov-02 Jan-03 Apr-03 Jul-03 Sep-03 Dec-03 Mar-04 May-04 Aug-04
Time (months)
Nitr
ate
Con
cent
ratio
n (m
g-N
/L)
H3 H4 V8 V9
MCL
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•Judson Lake
Study Area
Pangborn Bog
BC
WA
H-3
V-9
H-4
V-8
BC3BC4
BC5
BC6
The nitrate concentrations measured in BC wells are similar in magnitude to bordering WA wells
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BC Wells Near the Border
0
5
10
15
20
25
30
35
Mar-02 May-02 Aug-02 Nov-02 Jan-03 Apr-03 Jul-03 Sep-03 Dec-03 Mar-04 May-04 Aug-04
Time (months)
Nitr
ate
Con
cent
ratio
n (m
g-N
/L)
BC3 BC4 BC5 BC6
MCL
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Judson Lake
Study Area
Pangborn Bog
BCWA
T-1
V-5V-6
H-7
Shallow wells in the study area had the highest nitrate concentrations due to a combination of BC and Whatcom County sources
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Shallow Wells in the Study Area
0
5
10
15
20
25
30
35
40
45
Mar-02 May-02 Aug-02 Nov-02 Jan-03 Apr-03 Jul-03 Sep-03 Dec-03 Mar-04 May-04 Aug-04
Time (months)
Nitr
ate
Con
cent
ratio
n (m
g-N
/L)
H7 T1 V5 V6
MCL
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Shallow Wells in the Study Area
0
5
10
15
20
25
30
35
40
45
Mar-02 May-02 Aug-02 Nov-02 Jan-03 Apr-03 Jul-03 Sep-03 Dec-03 Mar-04 May-04 Aug-04
Time (months)
Nitr
ate
Con
cent
ratio
n (m
g-N
/L)
H7 T1 V5 V6
MCL
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Judson Lake
Study Area
Pangborn Bog
BCWA
K-1
P-1
P-2
P-3
Wells south of Pangborn Bog and the creek had low nitrate concentrations due to denitrification in the organic-rich peat
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Wells South of Pangborn Bog
0
5
10
15
20
25
30
35
31-May-02 19-Aug-02 8-Nov-02 27-Jan-03 17-Apr-03 6-Jul-03 24-Sep-03 13-Dec-03 2-Mar-04 21-May-04
Time (months)
Nitr
ate
Con
cent
ratio
n (m
g-N
/L)
K1 P1 P2 P3
MCL
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PANGBORN RD
HALVERSTIC RD
VAN
BU
REN
RD
HALVERSTIC RD
Judson Lake
Pangbor Lake
±0 0.5 1 1.50.25
Miles
0 0.5 1 1.50.25Kilometers
CANADA
UNITE STATES
LegendSoil Type
PUGET
SKIPOPA
SUMA S
TERRI MEDISAPR ISTS
TR OMP
WATER
WH ATCO M
PANGBORN
PANGBORN VARIANT
BRISCOT
CAGEY
EVER ETT
HALE
HISTOSOLS
KICKER VILLE
LABO UNTY
LAXT ON
ORIDIA
Soils Map(peat is blue)
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Peat has excellent denitrification potential
N S∆
denitrification
peat
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Peat has excellent denitrification potential
N S∆
denitrification
• high organic content
peat
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Peat has excellent denitrification potential
N S∆
denitrification
• high organic content
• reducing conditions
peat
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Peat has excellent denitrification potential
N S∆
denitrification
• high organic content
• reducing conditions
• iron and manganese
peat
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Peat has excellent denitrification potential
N S∆
denitrification
• high organic content
• reducing conditions
• iron and manganese
• nitrate input
peat
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Denitrification Evidence
N S∆
denitrification
• low nitrate concentrations
• low DO (< 1 mg N/L)
• enriched δ15N values (> 12 0/00)
• high ammonia (> 100 µg/L)
• excess N2 gas (2 to 10 mg/L)
nitrate 10 – 30 mg N/L
nitrate 0 – 10 mg N/L
peat
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∆ N S
It is likely that peat occurs at various depths due to multiple glacial phases during the Sumas Stade
BC WA
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Denitrification
Indicators such as low DO, high metals, and/or enriched δ15N values suggest denitrification at a variety of wells.
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0 10 20 30 40
02
46
810
12
Nitrate+Nitrite (mgN/L)
YS
I Dis
solv
ed O
xyge
n (m
g/L,
fiel
d m
eter
)
tau = 0.36pvalue <2.2e16
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N S
∆
Nitrate Concentration Stratification
The nitrate concentrations are higher near the water table because it’s closer to the surface sources (median of 15.7 mg N/L).
BC WA
Lower concentrations occur deeper in the aquifer because of mixing and dilution (median of 11.3 mg N/L).
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PANGBORN RD
HALVERSTIC RD
VAN
BU
REN
RD
HALVERSTIC RD
Judson Lake
Pangbor Lake
JN5
JN4JN3JN2
JN1
PB5
PB4PB3
PB2PB1
V9
T1P3
V6V5
V4
V1
H8H6H5H2
H1
V10
K1
V8
V7
V3
V2T2
P2
H7H4H3
V12
BC3BC6
BC5BC4
±0 0.5 1 1.50.25
Miles
0 0.7 1.4 2.10.35Kilometers
Legend
Deep Wells
Shallow Wells
Stream Sampling Sites
Streams
CANADA
UNITE STATES
Study Area
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05
1015
Site T2
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
Nitrate+NitriteDepth
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
2025
3035
40
Dep
th to
Wat
er (f
t)
irrigation well50 feet below the water table
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05
1015
Site T2
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
Nitrate+NitriteDepth
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
2025
3035
40
Dep
th to
Wat
er (f
t)
irrigation well50 feet below the water table
static water level
drawdown
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Judson Lake
Pangbor Lake
V9
T1
P3
V6V5
V4
V1
H8H6H5H2H1
V10
PANGBORN RD
HALVERSTIC RD
VAN
BU
RE
N R
D
HALVERSTIC RD
K1
V8V7
V3
V2T2
P2P1
H7H4H3
V12
±0 0.5 1 1.50.25
Miles
0 0.7 1.4 2.10.35Kilometers
Legend
Shallo Wells
Deep Wells
Rasp
blueberry
corn
grass
nuts
pasture
Crop Type (2003)
2
2 - 8
8 - 12
12
d 15 N 0/00
CANADA
UNITE STATES
Nitrogen Isotope values (δ15N) indicate animal N sources and mixed animal and commercial N sources.
Nitrogen Isotope Results (7/02 to 6/04)
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H1
H2
H3
H4
H5
H6
H7
H8 K1 P1
P2
P3 T1 T2 V1
V10
V11
V12 V3
V4
V5
V6
V7
V8
V9
0
5
10
15
20
25
30N
itrog
en Is
otop
e R
atio(
δ15N
,‰)
shallow wellsdeep wells
inorganic N source
organic N source
mixed N sources
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Judson Lake
Pangbor Lake
JN5
JN4JN3
JN2
JN1
PB5
PB4PB3
PB2PB1PANGBORN RD
HALVERSTIC RD
VAN
BU
REN
RD
HALVERSTIC RD
±0 0.4 0.8 1.20.2
Miles
0 0.7 1.4 2.10.35Kilometers
Stream Sampling Sites
Legend
CANADA
UNITE STATES
3
3 - 10
10 - 15
15 - 20
20
Nitrate m N/LRasp
blueberry
corn
grass
nuts
pasture
Crop Typ (2003)
Study Area – Surface Water
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JN1 JN2 JN3 JN4 JN5 PB1 PB2 PB3 PB4 PB5
510
15
Nitr
ate+
Nitr
ite (m
gN/L
)
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5 10 15
510
15
Total Nitrogen (mgN/L)
Nitr
ate+
Nitr
ite (m
gN/L
)
tau = 0.86pvalue < 2.2e16
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JN1 JN2 JN3 JN4 JN5 PB1 PB2 PB3 PB4 PB5
050
100
150
200
250
300
Am
mon
ia(µ
gN/L
)
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Study Area – Surface Water
Judson Lake
Pangbor Lake
JN5
JN4JN3
JN2
JN1
PB5
PB4PB3
PB2PB1PANGBORN RD
HALVERSTIC RD
VAN
BU
REN
RD
HALVERSTIC RD
±0 0.4 0.8 1.20.2
Miles
0 0.7 1.4 2.10.35Kilometers
Stream Sampling Sites
Legend
CANADA
UNITE STATES
3
3 - 10
10 - 15
15 - 20
20
Nitrate m N/LRasp
blueberry
corn
grass
nuts
pasture
Crop Typ (2003)
V4
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02
46
810
YS
I Dis
solv
ed O
xyge
n (m
g/L,
fiel
d m
eter)
2Jul2002 2Jul2003 1Jul2004
V4PB4
05
1015
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 2Jul2003 1Jul2004
V4PB4
050
100
Am
mon
ia (u
gN/L
)
2Jul2002 2Jul2003 1Jul2004
V4PB4
02
46
810
12
Chl
orid
e (m
g/L)
2Jul2002 2Jul2003 1Jul2004
V4PB4
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JN1 JN2 JN3 JN4 JN5 PB1 PB2 PB3 PB4 PB5
89
1011
12
Nitr
ogen
Isot
ope
Rat
io(δ15
N,‰
)
organic N source
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JN1 JN2 JN3 JN4 JN5 PB1 PB2 PB3 PB4 PB5
510
5010
050
050
00
Feca
l Col
iform
s (c
fu/1
00m
l)
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Conclusions
• Nitrate concentrations remain high in both surface water and groundwater in the study area.
• Nitrate concentrations transported across the border from BC range from about 10 to 25 mg-N/L and reflect a mix of manure and inorganic N sources.
• Nitrate concentrations in shallow wells in Washington range fromabout 15 to 35 mg-N/L and correlate to a combination of BC and local N sources.
• Denitrification is occurring in the peat in Pangborn Bog resulting in lower nitrate concentrations south of the bog.
• Denitrification is also occurring at other isolated locations.
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Resulting Works
Mitchell, R. and others, Abbotsford-Sumas Water Quality: Draft Final Report (http://kula.geol.wwu.edu/rjmitch/absum.html).
McKee, L. Denitrification along Pangborn Creek in the Abbotsford-Sumas Aquifer, Washington. M.S. Thesis, Western Washington University, Bellingham, WA, 2004.
Burton, M. Correlations between surface processes and groundwater nitrate concentrations in Northwestern Whatcom County, Washington. M.S. Thesis, Western Washington University, Bellingham, WA (expected 2006).
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1113
15
Site H1
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
1113
15
Site H2
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul20049
1011
12
Site H3
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
1011
1213
14
Site H4
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
910
1112
13
Site H5
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
1520
2530
35
Site H6N
itrat
e+N
itrite
(mgN
/L)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
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1020
3040
Site H7
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
1315
1719
Site H8
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul20044
68
10
Site K1
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
67
89
Site P1
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
3.0
4.0
5.0
Site P2
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
510
1520
Site P3N
itrat
e+N
itrite
(mgN
/L)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
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1618
2022
Site T1
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
68
1014
Site T2
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
2.0
3.0
4.0
Site V1
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
0.00
0.04
0.08
Site V2
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
2.0
2.5
3.0
Site V3
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
510
15Site V4
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
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05
1525
Site V5
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
1418
2226
Site V6
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
12
34
56
Site V7
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
1416
1820
Site V8
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
1618
2022
Site V9
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
78
910
Site V10N
itrat
e+N
itrite
(mgN
/L)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
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23
45
6
Site V11
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
0.2
0.4
0.6
Site V12
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004
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1416
1820
2224
26
Site BC3
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 2Jul2003 1Jul2004
46
810
1214
Site BC4
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 2Jul2003 1Jul2004
810
1418
22
Site BC5
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 2Jul2003 1Jul2004
2022
2426
Site BC6
Nitr
ate+
Nitr
ite (m
gN/L
)
2Jul2002 2Jul2003 1Jul2004
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D1 D2 D3 H5 K1 P1 P2 P3 S1 S2 S3 V4
0.0
e+00
5.0
e+06
1.0
e+07
1.5
e+07
2.0
e+07
Site
Sul
fate
Pea
k