Balancing Wildlife Needs and Nitrate Removal in Constructed Wetlands: The
Case of the Irvine Ranch Water District’s San Joaquin Wildlife Sanctuary.
Maia S. Fleming-Singera & Alexander J. Horne, Department of Civil & Environmental Engineering, #1710, University of California, Berkeley, CA 94720, USA
aCorresponding Author: Stillwater Sciences Inc. Berkeley, CA 94705, USA (510) 848-8098, FAX (510) 848-8398, [email protected]
Acknowledgements: Louis Denger, Irvine Ranch Water District; Nancy & Richard Kenyon, Sea & Sage Audubon; Mark Taylor, Hayward Shoreline Marsh.
Methods
14
14
12
12
1999
10
2. Avian Species Diversity and Abundance
8
6
10%
2
Monthly species abundance =
average combined bird density
(dabbling ducks + diving ducks +
shorebirds + fish-eating birds +
gulls + landbirds).
8
6
4
4
Bird census data collected and
reported by volunteer birders to the
Audobon Sea and Sage House
(http://exo.com/~kenyon/sjwsbirdlist
.htm).
Flow, water level & water quality
(WQ) data collected by IRWD
personnel. WQ data analyzed using
Standard Methods (APHA 1998) in
the IRWD certified laboratory.
mg N/L
mg N/L
10
1. Water
2001
0
5-Apr
25-May
14-Jul
14
2
2-Sep
40%
0
30-Mar
22-Oct
19-May
8-Jul
27-Aug
16-Oct
2002
12
10
mg N/L
Avian species diversity = number
of species observed each month,
where data available.
8
6
4
4-week running average (4-wk RA)
used to represent system behavior
for non-winter (April-October) data.
A
B
B
A
B
24-May
13-Jul
( AvgNO3 ) in
 kt

exp
( AvgNO3 ) out
21-Oct
250
Figure 5. Comparison of
SJWS Bird Density (±1 SE)
with Two Constructed
Wetlands in Northern CA.
Note the increase in numbers
during fall migration in the
Hayward Marsh, as compared
with the other two systems
which are relatively younger.
Mountain View Sanitary District 3-yr Avg
Hayward Marsh 4-5 yr Avg
Combined Bird Density (# ha-1)
Table 3. Results from Constructed Wetland Treatment System Bird Surveys.
San Joaquin Wildlife Sanctuary 4-yr Avg
Table amended from Kadlec & Knight, 1996. Sites are listed by increasing marsh area. Compared with several
other
150
treatment wetlands, counts at SJWS are high for total number of species observed and in the middle of the range for
state models.
averageApplication
annualof steady
density.
100
[( AvgNO3 )in  ( AvgNO3 )out ](mgN / L) 1,000( L / m3 )  AvgInflow(m3 / d )
Estimated _ Denitrific ation _ Rate 
AvgTotBottomArea(m2 )
1-Sep
Figure 4. Comparison of TN Removal to Algal Nitrogen
Produced in SJWS. 4-wk RA TN and Chl-a data (expressed as N in
algal biomass). Chl-a data was not available for Summer 2000. The
amount of algal-N produced at SJWS as a fraction of TN removed was at
its greatest (10-40%) during July and August of each year.
200
50
0
where k is the first order rate constant (d-1) for nitrate removal and t is the average HRT (d).
J
F
M
A
M
J
J
A
S
O
N
D
Table modifed from Kadlec, R. H. and R. L. Knight 1996. Treatment Wetlands.
Boca Raton, Florida, Lewis Publishers, 893 p.
Results
Ponds 1 & 2 amended with
barnyard grass
12
Org-N
Org-N
NH4+
NH3
NO2-+NO3NO2/NO3
10
1999
2000
2001
2002
2
Estimated Denitrification Rate (mg/m /d)
(a)
No grass
amendments
500
400
300
aMcAllister
1993a
1999
chttp://exo.com/~kenyon/sjwsbirdlist.htm
dTaylor, pers. Comm.
eRange rather than average data was available for this site. McAllister 1993b
bEPA
200
100
0
30-Mar
8
6
(47%)
(60%)
(52%)
4
(69%)
2
0
In
Out
In Out
1999
Table 1. Compared with several
other treatment wetlands, species
diversity at SJWS was high while
average annual density was midrange.
600
In
2000
Out
2000
In
2001
Out
2001
In
2002
Out
2002
1999
Figure 2. Relative Amounts of Three Major
Nitrogen Species Entering and Leaving SJWS 19992002. TN removal is shown in parentheses for each year.
Across all four years, average TN removal was 56±1%
(±1SE). Note there is no discernable difference between
amended and non-amended conditions. NO2-+NO3- was
the greatest fraction of wetland inlet N, while Org-N was
the greatest fraction of total outlet N except in 2001,
when it was roughly equal to NO2-+NO3-.
19-May
8-Jul
27-Aug
(b)
600
y = 52.3x - 51.2
R2 = 0.94
Series1
1999
2000
Series2
Series3
2001
Series4
2002
500
400
16-Oct
y = 28.3x + 73.8
R2 = 0.67
300
y = 23.3x + 40.8
R2 = 0.80
200
100
0
0
5
10
Conc. [NO2-+NO3-](mg/l)
15
Site
Collins, MSa
Ocean Springs, MSa
Mountain View Sanitary
District, Martinez, CAb
San Joaquin Wildlife
Sanctuary, Irvine, CAc
Hayward Marsh, CA
Incline Village, NVa
Show Low, AZa
Lakeland, FL
Figure 3. Calculated Non-Winter
Denitrification in SJWS. 4-wk RA (a)
nitrate removal rates and (b) the relationship
between estimated denitrification rates and
inlet nitrate. Denit. rates correlated well with
inlet NO2-+NO3- concentrations. First order
rate constants [k(20°C)] are not shown in the
figures, however they ranged 0.05-0.25 d-1.
Estimated Denitrification Rate (mg/m /d)
A
Figure 1. Location
Map 33o 39' 18"N; 117o
50' 41" E, near San
Diego Creek inlet to
upper Newport Bay, CA.
Pumped flow shown by
arrows, indicating
approximate locations for
inlet and outlet of each
pond. Ponds A and B are
initial holding ponds.
Water levels in Ponds 3 &
4 fluctuate on a biweekly basis to provide
habitat for shorebirds.
30%
0
4-Apr
The 4-wk RA incorporates information about system dynamics without being
overwhelmed by extremes of changing pond volumes occurring on smaller time scales.
SJWS design perturbations invalidate the application of simplified reactor models which
on a weekly time scale. Simple models use inlet and outlet parameters and the
assumption of steady state behavior to describe wetland performance. Although more
complex versions of the reactor models can be applied under non-steady state
conditions (Kadlec and Knight 1996), accurate knowledge of flow and volume
fluctuations is required for all modeling periods; a requirement that was not met for the
SJWS.
2
The San Joaquin Wildlife Sanctuary (SJWS), Irvine CA,
is a 32-ha series of shallow ponds owned and operated
by the Irvine Ranch Water District (IRWD). SJWS was
created to maximize nitrogen removal rates while still
maintaining 90% open water and episodically exposed
shoreline for waterfowl, shorebird and wading bird
habitat. These avian design elements created non-ideal
denitrification conditions in the marsh by diminishing an
important source of organic carbon (emergent
vegetation) and increasing sediment exposure to
oxygen. Seasonal plantings of barnyard grass (E.
crusgalli) in two of the largest ponds were intended to
serve as a carbon amendment for denitrification. We
show SJWS aqueous nitrogen and avian data for nonwinter months 1999-2002, analyzed to determine
whether design and operating conditions allowed for
simultaneous nitrogen removal and diverse, abundant
avian habitat.
Avg Conc for Non-Winter Months (mg/l)
Background
2
Rationale for averaging period:
The chosen metric is approximately:
• 2x the typical hydraulic residence time of water (HRT=10-14 days);
• 2x the most frequent volumetric perturbation period (approx bi-weekly);
• 0.2x the seasonal time scale of interest (28-weeks of non-winter months).
20
Year
Sampled
1991
1991
1989-1991
1999
2000
2001
2002
1989b
2000d
2001d
2002d
1991
1991
1991
Constructed
Wetland Area Total Bird
(ha)
Species
4.5
35
22
35
34
123
32
70
198
284
498
147
98
136
156
94
ND
ND
ND
47
42
63
Average
Annual
Density
(#/ha)
7
10
21
71
57
71
65
54
108
79
68
19
14
(7.7-13.5)e
Conclusions
• Avian design features did not appear to inhibit high rates
of denitrification in SJWS during 1999-2002. Overall, SJWS
met its dual design objectives of high TN removal (56±1%)
and the creation of diverse, abundant avian habitat.
• During 1999-2002, barnyard grass amendments did not
appear to enhance N-removal.
• Low levels of Org-N were produced in SJWS, and algal-N
production was greatest relative to TN-removed in July and
August of each year.