tetra tech, inc. conceptual models for constituents of drinking water concern in the central valley...
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TETRA TECH, INC.
Conceptual Models for Constituents of Drinking Water Conceptual Models for Constituents of Drinking Water Concern in the Central Valley and Delta: Organic Carbon, Concern in the Central Valley and Delta: Organic Carbon,
Nutrients and PathogensNutrients and Pathogens
Prepared for:US Environmental Protection Agency, Region IX
and
Central Valley Drinking Water Policy Workgroup
Sujoy Roy, Katherine Heidel, Clayton Creager, Chih-Fang Chung, and Tom Grieb
Tetra Tech, Inc.Lafayette, CA
TETRA TECH, INC.
Overview
Goals of conceptual model development Provide a summary of key results from
conceptual model development for: Organic carbon Nutrients Pathogens and pathogen indicators
(ongoing) Recommendations for future monitoring
and modeling
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Why these Constituents Matter
Organic carbon: A precursor for trihalomethanes and haloacetic acids during chlorine disinfection. These are carcinogenic, and regulations require very low concentrations in treated drinking water.
Nutrients: Can increase algae growth, some species of which can impart taste and odor, others produce toxins. Excess nutrients can result in elevated organic carbon in water supplies.
Pathogens: Removal of these is the primary goal of water treatment.
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Geographic Setting
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Role of the Conceptual Models
Using existing data, summarize current understanding of the behavior of the selected constituents in the Central Valley and Delta
Particular focus on magnitudes of different sources and transport in the Central Valley and Delta
Communicate information to wide audience: illustrate key assumptions and processes; identify data gaps
Provide technical basis for future planning: identify data, analysis and modeling needs
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Organic Carbon Transport in the Central Valley-Delta Ecosystem
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Organic Carbon in the Aquatic Environment
OC can exhibit an wide range of age and bioavailability to organisms, a property independent of reactivity to form DBPs
POC more available than DOC; DOC less important to the food web
OC derived primary production more bioavailable and considered a higher-quality food source
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TOC Concentrations
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Wet Year (2003) Flows
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Load Calculation Approach
Monthly average concentration
x Monthly average flow
=
Monthly load
American River
Month
Jan
(4
)
Fe
b (
4)
Ma
r (4
)
Ap
r (3
)
Ma
y (3
)
Jun
(3
)
Jul (
1)
Au
g (
4)
Se
p (
3)
Oct
(2
)
No
v (3
)
De
c (4
)
Ave
rage
TO
C (
mg
/l)
0
1
2
3
4
5
American River
Year
1980 1985 1990 1995 2000 2005
Da
ily F
low
, cf
s
0
20000
40000
60000
80000
100000
120000
140000
American River
Water Year
1980 1985 1990 1995 2000 2005
TO
C L
oa
d,
ton
s
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
20000
Dry Season
Wet Season
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Organic Carbon Loads Dry and Wet season (Wet Year)
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Using Land-Use Specific Export Rates
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Export Rates of Organic Carbon from Major Land Uses in the Central Valley
Dry Year Loads (tons/km2/yr)
Wet Year Loads (tons/km2/yr)
Source Land Use
Sac-ramento
San Joaquin
Sac-ramento
San Joaquin
Sacramento San Joaquin
Agriculture1 0.56 1.9 1.6 2.6 Colusa Basin Drain Harding Drain2
Urban Runoff 1.3 0.67 2.4 1.2 Arcade Creek Calculated from
Sacramento value
Forest/Rangeland 0.41 0.21 1.7 0.85 Yuba River Calculated from
Sacramento value
Wetland-Dominated3 1.4 0.69 2.0 1.0 Calculated from
San Joaquin value Average of Salt and
Mud Slough 1Available data do not allow separation into crop types. 2May include a small POTW influence. 3Wetland-dominated land may include a portion that is agricultural land.
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Stream Reach Load Diagram
Loads Exported Downstream
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Organic Carbon Watershed Loads by SourceDistribution of Inflow Loads by Watershed, Wet Years
TO
C L
oad
(ton
s/ye
ar)
0
10000
20000
30000
40000
AgricultureUrban RunoffForest/RangelandWetlandsPoint Sources
Inflow and Outflow Loads by Watershed, Wet Years
Sac
ram
ento
R. a
t Ben
d B
ridge
But
te C
r. *
Sac
ram
ento
R. a
t Col
usa
Yub
a R
.
Bea
r R
.
Fea
ther
R.
Am
eric
an R
.
Sac
ram
ento
R. a
t Hoo
d/G
r. L
andi
ng
Cac
he C
r.
Put
ah C
r. *
San
Joa
quin
R. a
t Sac
k D
am *
Cho
wch
illa
R. *
Bea
r C
r. *
Mer
ced
R. *
San
Joa
quin
R. a
t New
man
Tuo
lum
ne R
.
Sta
nisl
aus
R.
San
Joa
quin
R. a
t Ver
nalis
Cos
umne
s R
.
Mok
elum
ne R
.
Del
ta N
orth
*
Del
ta S
outh
*
TO
C L
oad
(ton
s/ye
ar)
100
1000
10000
100000
1000000Watershed LoadsWatershed Loads + Upstream InputsOutflows
* Outflows equal inflows;no independent measurements
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Summary of Organic Carbon Loads from the Delta Watershed
Dry Year Loads
TO
C L
oad
(to
ns/y
ear)
0
20000
40000
60000
80000
100000
AgricultureUrban RunoffForest/RangelandWetlands Point Sources
Wet Year LoadsS
acra
men
to a
t Hoo
d/G
reen
e's
San
Joa
quin
at V
erna
lis
TO
C L
oad
(to
ns/y
ear)
0
20000
40000
60000
80000
100000
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Delta Organic Carbon Loads
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Concentrations at Key Delta Stations
Date
1/90 1/91 1/92 1/93 1/94 1/95 1/96 1/97 1/98 1/99 1/00 1/01 1/02 1/03 1/04 1/05
DO
C (
mg/
l)
0
2
4
6
8
10
12Sacramento R at Hood/Greene's Landing
San Joaquin River at Vernalis Banks Intake
Dry Year Wet Year
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DWR DSM2 Model Fingerprinting Results
Modeled DOC Fingerprint at Banks Pumping Plant
0
1
2
3
4
5
7/1/
2005
8/1/
2005
9/1/
2005
10/1
/200
5
11/1
/200
5
12/1
/200
5
1/1/
2006
DO
C S
ou
rce
Co
ntr
ibu
tio
ns
, mg
/L
DOC-SAC DOC-SJR DOC-EAST DOC-Delta DOC
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What Did We Learn and How Can We Use It? Dry year loads for the Sacramento and San Joaquin Rivers are
similar, although in wet years, the Sacramento River is a much greater contributor.
There are many streams in the Central Valley for which organic carbon data were not available or are very limited. Some of these data gaps have been filled through ongoing efforts, and some locations may need additional monitoring.
Land-use specific export rates, especially for different agricultural practices and undeveloped lands, has the potential to improve the accuracy of source characterization, and should be considered for refinement.
Organic carbon exports from forested watersheds in the wet seasons can be a significant source, not very different from agricultural lands.
Although organic carbon chemical characterization has the potential to more closely relate it to THM formation potential, the data that do exist are limited spatially and temporally. Given the inter- and intra-year variability of flows and loads in the Delta, greater coverage of such analysis is strongly recommended. 20
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Nutrients Conceptual Model
Emphasis is on nitrogen and phosphorus Usually, the impact of nutrients on drinking water
quality is indirect, and occurs through increased primary productivity, with the potential for higher TOC, taste/odor and toxin concerns (Exception: Nitrate and nitrite)
Nutrient impacts are more likely to express themselves during transport in aqueducts and storage in reservoirs, that at the intakes.
The conceptual model looked at nutrient loads and concentrations, not on the secondary indicators
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Nutrient Species
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Total Nitrogen
Sacramento River Downstream
Ke
swic
k -
96
Ab
ove
Be
nd B
rid
ge
- 2
6
Co
lusa
- 3
3
Ve
ron
a -
28
Fre
epo
rt -
223
Ho
od-
Gre
ene'
s La
ndin
g -
406
Ab
ove
Po
int
Sac
ram
en
to -
352
Mal
lard
Isl
and
- 3
2
TK
N (
mg
/l)
0.01
0.1
1
10Delta
San Joaquin River Downstream
Ste
vin
son
- 5
8
Ne
wm
an
- 5
4
Cro
ws
La
nd
ing
- 2
8
Pa
tte
rso
n -
74
Ma
ze R
d B
rid
ge
- 5
1
Ve
rna
lis -
73
6
Hw
y 1
20
- 2
76
Bu
ckle
y C
ove
- 3
53
Po
tato
Po
int
- 3
55
Jers
ey
Po
int
- 2
66
TK
N (
mg/
l)
0.01
0.1
1
10Delta
Sacramento
San Joaquin
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Total Phosphorus
Sacramento River Downstream
Ke
swic
k -
10
8
Ab
ove
Be
nd
Bri
dg
e -
26
Wo
od
son
Bri
dg
e -
39
Co
lusa
- 4
9
Kn
igh
ts L
an
din
g -
10
2
Fre
ep
ort
- 3
37
Ho
od
-Gre
en
e's
La
nd
ing
- 3
27
Ab
ove
Po
int
Sa
cra
me
nto
- 2
75
Ma
llard
Isl
an
d -
32
To
tal P
hosp
horu
s (m
g/l)
0.001
0.01
0.1
1
Delta
San Joaquin River Downstream
Hw
y 1
65 -
10
1
Ne
wm
an
- 5
5
Cro
ws
La
nd
ing
- 28
Pa
tte
rso
n -
16
3
Hw
y 1
32 -
10
1
Ve
rna
lis -
717
Hw
y 1
20 -
28
9
Bu
ckle
y C
ove
- 2
75
Po
tato
Po
int
- 2
77
Jers
ey
Poi
nt
- 1
88
Tot
al P
hosp
horu
s (m
g/l)
0.001
0.01
0.1
1
Delta
Sacramento
San Joaquin
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Total Nitrogen
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Total Phosphorus
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Nitrogen and Phosphorus Loads by Watershed and Source
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Nutrient Loads Entering and Leaving the Delta
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Nitrogen Species Concentrations in the Delta
0
1
2
3
4
5
6
Oct
-79
Oct
-80
Oct
-81
Oct
-82
Oct
-83
Oct
-84
Oct
-85
Oct
-86
Oct
-87
Oct
-88
Oct
-89
Oct
-90
Oct
-91
Oct
-92
Oct
-93
Oct
-94
Oct
-95
Oct
-96
Oct
-97
Oct
-98
Oct
-99
Oct
-00
Oct
-01
Oct
-02
Oct
-03
Date
Nir
ate
+ N
itri
te -
N (
mg
/l)
Sacramento at Hood/Greene's LandingSan Joaquin River at VernalisBanks Pumping Plant
0
0.4
0.8
1.2
1.6
Oct
-79
Oct
-80
Oct
-81
Oct
-82
Oct
-83
Oct
-84
Oct
-85
Oct
-86
Oct
-87
Oct
-88
Oct
-89
Oct
-90
Oct
-91
Oct
-92
Oct
-93
Oct
-94
Oct
-95
Oct
-96
Oct
-97
Oct
-98
Oct
-99
Oct
-00
Oct
-01
Oct
-02
Oct
-03
Date
Am
mo
nia
- N
(m
g/l)
Sacramento at Hood/Greene's LandingSan Joaquin River at VernalisBanks Pumping Plant
0
1
2
3
4
Oct
-79
Oct
-80
Oct
-81
Oct
-82
Oct
-83
Oct
-84
Oct
-85
Oct
-86
Oct
-87
Oct
-88
Oct
-89
Oct
-90
Oct
-91
Oct
-92
Oct
-93
Oct
-94
Oct
-95
Oct
-96
Oct
-97
Oct
-98
Oct
-99
Oct
-00
Oct
-01
Oct
-02
Oct
-03
Date
To
tal K
jeld
ahl N
itro
gen
(m
g/l)
Sacramento at Hood/Greene's LandingSan Joaquin River at VernalisBanks Pumping Plant
0
0.4
0.8
1.2
1.6
Oct
-79
Oct
-80
Oct
-81
Oct
-82
Oct
-83
Oct
-84
Oct
-85
Oct
-86
Oct
-87
Oct
-88
Oct
-89
Oct
-90
Oct
-91
Oct
-92
Oct
-93
Oct
-94
Oct
-95
Oct
-96
Oct
-97
Oct
-98
Oct
-99
Oct
-00
Oct
-01
Oct
-02
Oct
-03
0
2
4
6
8
10
Oct
-79
Oct
-80
Oct
-81
Oct
-82
Oct
-83
Oct
-84
Oct
-85
Oct
-86
Oct
-87
Oct
-88
Oct
-89
Oct
-90
Oct
-91
Oct
-92
Oct
-93
Oct
-94
Oct
-95
Oct
-96
Oct
-97
Oct
-98
Oct
-99
Oct
-00
Oct
-01
Oct
-02
Oct
-03
Date
To
tal N
itro
gen
(m
g/l)
Sacramento at Hood/Greene's LandingSan Joaquin River at VernalisBanks Pumping Plant
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What Did We Learn and How Can We Use It?
Point sources are a major contributor of nutrients, and in dry years, can constitute more than 50% of the total loads.
Exports from forested land/rangeland in the wet seasons are a significant source, often larger than point source loads in the wet season. Improved estimates of land-use specific export rates, especially for different agricultural practices and undeveloped lands are needed, as noted earlier for organic carbon.
Concentrations of nitrogen and phosphorus in the Delta are indicative of eutrophic waters, although the primary productivity is not as high, likely due to light limitation because of suspended solids. Concentrations of nutrients at the Banks Intake are relatively uniform over different years and seasons.
When Delta waters are extracted and transported long distances or stored, suspended particles can settle out, reducing the light limitation and enhancing algal productivity. This can lead to adverse impacts on drinking water quality. More research of behavior of Delta water after withdrawal is needed.
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Pathogens and Pathogen Indicators
Most available data is for indicator organisms: total coliforms, fecal coliforms, and E. Coli
Limited data on Cryptosporidum and Giardia Although it is understood that specific pathogens
may be more long-lived than indicator coliforms, there is no consensus on alternate indicators
Of necessity, the pathogen conceptual model (now in progress) will be less quantitative than conceptual models for organic carbon and nutrients
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Pathogen Indicators
E. Coli Fecal Coliforms
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Total Coliform Counts in
Wastewater Discharge
Total Coliform (MPN/100 mL)
1 10 100 1000 10000
Loca
tion
Brentwood-effluent - 51
Chico-effluent - 59
City of Brentwood WWTP-Effluent 003 - 7
City of Manteca WWQCF-Effluent - 54
City of Modesto WQCF-Effluent - 27
City of Tracy WWTP-Effluent - 58
Davis-effluent - 23
Davis-effluent1 - 8
Discovery Bay-effluent - 47
Dry Creek WWTP (Roseville)-Effluent - 53
Lodi-effluent - 46
Merced-effluent - 59
Pleasant Grove WWTP (Roseville)-Effluent - 6
Red_NPD_Clr-Redding-effluent - 19
Red_NPD_Stll-Redding-effluent - 56
Sacramento Regional WWTP Outfall - 1455
Stockton-effluent - 59
Turlock-effluent - 55
Vacaville-Effluent - 36
Woodland-effluent - 57
Yuba-effluent - 42
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Total Coliform Counts at
Runoff Locations
Stormwater
Total Coliform (MPN/100 mL)
103 104 105 106 107 108
Loca
tion
Calaveras River at 4250 North West Lane - 13
Calaveras River at CR45 - 12
Duck Creek at 555 Zephyr Drive - 15
Mosher Slough at 9211 Kelly Drive - 13
Mosher Slough at MS18 - 12
Strong Ranch Slough - 17
Sump 104 - 26
Sump 111 - 26
Dry weather
Total Coliform (MPN/100 mL)
103 104 105 106 107 108
Loca
tion
Calaveras River at 4250 North West Lane - 12
Duck Creek at 555 Zephyr Drive - 5
Mosher Slough at 9211 Kelly Drive - 5
Smith Canal at 840 Baker Place - 5
Strong Ranch Slough - 8
Sump 104 - 10
Sump 111 - 10
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Summary
Conceptual models present a synthesis of the magnitudes and variability of loads of different constituents from different sources
Highlight data gaps in data and understanding, and identify uncertainties that need to be reduced
Suggest needs for additional data collection, mechanistic modeling, and analysis
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Data/Modeling Needs for Selected Constituents
Monitor indicator watersheds to get better estimates of export rates from specific land uses
Agricultural drain maps to improve resolution of agricultural sources
More reservoir data to calculate reservoir exports of organic carbon
Quantification of flows from Delta agricultural drainage Better quantification of tidal marsh exports through ongoing
studies For wastewater sources, evaluate differences by process
type Mechanistic modeling of processes in Delta using DSM:
consider modeling nutrients Modeling of nutrient processes following withdrawal from
Delta
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