an evaluation of water quality modeling used to … evaluation of water quality modeling used to...
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An Evaluation of Water Quality Modeling Used to Inform Operational Decisions for the NYC Water Supply
Mark S. Zion, Donald C. Pierson and Elliot M. SchneidermanNew York City Department of Environmental Protection
Watershed Science and Technical ConferenceSeptember 13-14, 2012West Point, New York
Adao H. MatonseCUNY Institute for Sustainable Cities
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Introduction
• DEP has developed an extensive suite of water quality and water system models which are used to analyze turbidity transport in the Catskill System.
• Elevated turbidity can be an issue for the Catskill System of the NYC water supply during and after periods of high streamflow.
• During recent storm events, DEP’s water quality and water system models were used to help inform operational decisions and reduce turbidity entering the water distribution system.
• Informed use of operations during event periods can help to mitigate the impacts of turbidity on the water supply
• How well does the modeling system work in predicting the range in future turbidity which is subsequently used to inform operations?
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System Description
Kensico
Ashokan Reservoir OptionsD
IVID
ING
WEI
R
EAST BASIN
WESTBASIN
RELEASECHANNELCATSKILL
AQUEDUCT
GATEHOUSE
DIVIDINGWEIRGATE
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Model Description
Kensico
CEQUAL-W2 Two Dimensional Reservoir ModelsAshokan
Esopus Creek
DividingWeir
CatskillAqueduct
ReleaseChannel
Spillway
Catskill Influent
Catskill Effluent
Delaware Effluent
Delaware Influent
• CEQUAL-W2 Models adapted to simulate turbidity transport by Upstate Freshwater Institute (UFI).
• Models are connected using OASIS-W2 combined modeling software and applied in a positional analysis mode.
• Linked models can also be run using LinkRes software developed by UFI and adapted for positional analysis by DEP.
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Catskill Influent
Catskill Effluent
Delaware Effluent
Delaware Influent
Model Description
Kensico
Turbidity Profile
CEQUAL-W2 Two Dimensional Reservoir ModelsExample Longitudinal Profiles
Temperature
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Model DescriptionOASIS system model combined with CEQUAL-W2 Reservoir Models
• OASIS Model used to simulate aqueduct flows and reservoir releases and spills
• Combined OASIS-W2 is backbone of Operations Support Tool (under development)
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Reservoir Water Quality Model(CEQUAL-W2)
Meteorologic Input(Temp., RH, Solar Rad) Flows
OASIS Water System Model
Turbidity
Reservoir Storage
Effluent Turbidity
Initial Conditions(Reservoir Water
Temperature/Turbidity Profiles; Reservoir
Storage Levels;Snowpack)
Time Series Input (Forecast)
Initial Conditions (Snapshot)
Model
Results
Model Description – Application Method
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Reservoir Water Quality Model(CEQUAL-W2)
Meteorologic Input(Temp., RH, Solar Rad) Flows
OASIS Water System Model
Turbidity
Reservoir Storage
Effluent Turbidity
Initial Conditions(Reservoir Water
Temperature/Turbidity Profiles; Reservoir
Storage Levels;Snowpack)
Time Series Input (Forecast)
Initial Conditions (Snapshot)
Model
Results
Model Description – Application Method
• Current reservoir water surface elevations
• Limnological surveys• Data from automated
profiles of water column temperature and turbidity
• Snow survey results
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Reservoir Water Quality Model(CEQUAL-W2)
Meteorologic Input(Temp., RH, Solar Rad) Flows
OASIS Water System Model
Turbidity
Reservoir Storage
Effluent Turbidity
Initial Conditions(Reservoir Water
Temperature/Turbidity Profiles; Reservoir
Storage Levels;Snowpack)
Time Series Input (Forecast)
Initial Conditions (Snapshot)
Model
Results
Model Description – Application Method
• Forecast based on historical record or weather service analysis• Multiple traces representing many potential future input time series
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Reservoir Water Quality Model(CEQUAL-W2)
Meteorologic Input(Temp., RH, Solar Rad) Flows
OASIS Water System Model
Turbidity
Reservoir Storage
Effluent Turbidity
Initial Conditions(Reservoir Water
Temperature/Turbidity Profiles; Reservoir
Storage Levels;Snowpack)
Time Series Input (Forecast)
Initial Conditions (Snapshot)
Model
Results
Model Description – Application Method
Multiple time series results representing each of the forecast traces
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Model run for 57 inflow traces based on historical flow and meteorologic record (1948-2004)
Statistics of traces can be translated to cumulative probability function
Model Description – Application MethodExample of Positional Analysis
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Case Study – Late December 2011
• These simulations are run to provide an estimate of the time that it might take for Ashokan Reservoir turbidity to reduce to a level at which alum use would no longer be necessary.
• In late August and early September, Tropical Storms Irene and Lee greatly impacted turbidity in the Ashokan and Schoharie Reservoirs and alum use was initiated on Catskill inflow to Kensico Reservoir.
• At the time of these model runs in late December 2011, the impact on the Catskill system was still significant.
• On December 20 Ashokan turbidity ranged from 22-170 NTU. Schoharie turbidity on December 14 ranged from 45-60 NTU.
• Alum continued to be used to reduce impact of turbidity entering Kensico Reservoir. In addition, the Catskill Aqueduct flow was reduced through the use of stop shutters.
Schoharie Reservoir, Jan 5, 2012
• Simulations consisted of integrated OASIS/W2 model run.
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Ashokan Reservoir – Water Surface ElevOST Simulations of Dec. 20, 2011
Ashokan Reservoir – East Basin
Ashokan Reservoir – West Basin
Date
Individual Traces
Median
10th and 90th
Percentiles
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Ashokan Reservoir – Water Surface ElevOST Simulations of Dec. 20, 2011 vs. Actual Elevation
Ashokan Reservoir – East Basin
Ashokan Reservoir – West Basin
Date
Individual Traces
Median
10th and 90th
Percentiles
Recorded Elevation 2012
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Schoharie Reservoir ResultsOST Simulations of Dec. 20, 2011 vs. Keypoint Data
Shandaken Tunnel
Date
Individual Traces
Median
10th and 90th Percentiles
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Schoharie Reservoir ResultsOST Simulations of Dec. 20, 2011 vs. Keypoint Data
Shandaken Tunnel
Date
Individual Traces
Median
10th and 90th Percentiles
Keypoint Data - Shadaken Tunnel Portal
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Ashokan Reservoir – West Basin ResultsOST Simulations of Dec. 20, 2011 vs. Keypoint Data
Ashokan West Basin Entering Dividing Weir Gate
Date
Individual Traces
Median
10th and 90th Percentiles
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Ashokan Reservoir – West Basin ResultsOST Simulations of Dec. 20, 2011 vs. Keypoint Data
Ashokan West Basin Entering Dividing Weir Gate
Date
Individual Traces
Median
10th and 90th Percentiles
Keypoint Data - West Basin Gate House (middle level)
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Ashokan Reservoir – East Basin ResultsOST Simulations of Dec. 20, 2011 vs. Keypoint Data
Turbidity Ashokan East Basin near Gate House
Date
Individual Traces
Median
10th and 90th Percentiles
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Ashokan Reservoir – East Basin ResultsOST Simulations of Dec. 20, 2011 vs. Keypoint Data
Turbidity Ashokan East Basin near Gate House
Date
Individual Traces
Median
10th and 90th Percentiles
Keypoint Data - East Basin Gate House
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Ashokan Reservoir – Water Surface ElevOST Simulations of Dec. 20, 2011 vs. Actual Elevation
Ashokan Reservoir – East Basin
Ashokan Reservoir – West Basin
Date
Individual Traces
Median
10th and 90th
Percentiles
Recorded Elevation 2012
22
Ashokan Reservoir – Water Surface ElevOST Simulations of Dec. 20, 2011 vs. Actual Elevation
Ashokan Reservoir – East Basin
Ashokan Reservoir – West Basin
Date
Individual Traces
Median
10th and 90th
Percentiles
Recorded Elevation 2012
23
Schoharie Reservoir ResultsOST Simulations of Dec. 20, 2011 vs. Keypoint Data
Shandaken Tunnel
Date
Individual Traces
Median
10th and 90th Percentiles
Keypoint Data - Shadaken Tunnel Portal
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Schoharie Reservoir ResultsOST Simulations of Dec. 20, 2011 vs. Keypoint Data
Shandaken Tunnel
Date
Individual Traces
Median
10th and 90th Percentiles
Keypoint Data - Shadaken Tunnel Portal
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Ashokan Reservoir – West Basin ResultsOST Simulations of Dec. 20, 2011 vs. Keypoint Data
Ashokan West Basin Entering Dividing Weir Gate
Date
Individual Traces
Median
10th and 90th Percentiles
Keypoint Data - West Basin Gate House (middle level)
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Ashokan Reservoir – West Basin ResultsOST Simulations of Dec. 20, 2011 vs. Keypoint Data
Ashokan West Basin Entering Dividing Weir Gate
Date
Individual Traces
Median
10th and 90th Percentiles
Keypoint Data - West Basin Gate House (middle level)
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Ashokan Reservoir – East Basin ResultsOST Simulations of Dec. 20, 2011 vs. Keypoint Data
Turbidity Ashokan East Basin near Gate House
Date
Individual Traces
Median
10th and 90th Percentiles
Keypoint Data - East Basin Gate House
28
Ashokan Reservoir – East Basin ResultsOST Simulations of Dec. 20, 2011 vs. Keypoint Data
Turbidity Ashokan East Basin near Gate House
Date
Individual Traces
Median
10th and 90th Percentiles
Keypoint Data - East Basin Gate House
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Esopus Creek Inflow
Esopus Creek Turbidity
Case Study – Late March 2010
Catskill Influent
Catskill Effluent
Delaware Effluent
Delaware Influent
(30, 40 or 50 NTU)(50, 100, 150 or 600 MGD)
(1050, 1000, 950 or 900 MGD)
(1.5 NTU)
(400 MGD)
(700 MGD)
• A large rain and snowmelt event occurred on March 22, leading to elevated turbidity in Ashokan Reservoir.
• Stop shutters were installed in the Catskill Aqueduct to permit reduced flows from Catskill into Kensico Reservoir.
• What aqueduct flow rates should be used based on potential turbidity inputs from the Ashokan diversion?
• Kensico CEQUAL-W2 reservoir model is used to determine effects of elevated turbidity at various Catskill Aqueduct flow rates on Kensico Reservoir effluent.
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Reservoir Water Quality Model(CEQUAL-W2)
Meteorologic Input(Temp., RH, Solar Rad)
Flows Turbidity
Effluent Turbidity
Initial Conditions(Reservoir Water
Temperature/Turbidity Profiles)
Time Series Input (Forecast)
Initial Conditions (Snapshot)
Model
Results
Model Description – Application MethodKensico Sensitivity Model Application
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Reservoir Water Quality Model(CEQUAL-W2)
Meteorologic Input(Temp., RH, Solar Rad)
Flows Turbidity
Effluent Turbidity
Initial Conditions(Reservoir Water
Temperature/Turbidity Profiles)
Time Series Input (Forecast)
Initial Conditions (Snapshot)
Model
Results
Model Description – Application MethodKensico Sensitivity Model Application
• Current reservoir water surface elevations
• Limnological surveys• Data from automated
profiles of water column temperature and turbidity
32
Reservoir Water Quality Model(CEQUAL-W2)
Meteorologic Input(Temp., RH, Solar Rad)
Flows Turbidity
Effluent Turbidity
Initial Conditions(Reservoir Water
Temperature/Turbidity Profiles)
Time Series Input (Forecast)
Initial Conditions (Snapshot)
Model
Results
Model Description – Application MethodKensico Sensitivity Model Application
• Forecast based on historical record or weather service analysis• Multiple traces representing many potential future input time series
33
Reservoir Water Quality Model(CEQUAL-W2)
Meteorologic Input(Temp., RH, Solar Rad)
Flows Turbidity
Effluent Turbidity
Initial Conditions(Reservoir Water
Temperature/Turbidity Profiles)
Time Series Input (Forecast)
Initial Conditions (Snapshot)
Model
Results
Model Description – Application MethodKensico Sensitivity Model Application
Prescribed constant time series based on expected turbidity and potential flow rates from upstream reservoirs (via aqueducts)
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Reservoir Water Quality Model(CEQUAL-W2)
Meteorologic Input(Temp., RH, Solar Rad)
Flows Turbidity
Effluent Turbidity
Initial Conditions(Reservoir Water
Temperature/Turbidity Profiles)
Time Series Input (Forecast)
Initial Conditions (Snapshot)
Model
Results
Model Description – Application MethodKensico Sensitivity Model Application
For each combination of fixed turbidity and flow inputs the model produces multiple traces of turbidity results based on the meteorologic input traces
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Kensico Analysis Results – March 25, 2010Simulated Delaware Effluent Turbidity
30 NTU
Catskill Aqueduct Influent TurbidityCatskillAqueduct
Inflow
50 MGD
100 MGD
200 MGD
50 NTUTu
rbid
ity (N
TU)
Turb
idity
(NTU
)Tu
rbid
ity (N
TU)
Date Date
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Influent Turbidity
Inflows
Catskill Aqueduct Delaware Aqueduct
Kensico Results - ComparisonCatskill Aqueduct Input Chosen for Comparison: 30 NTU @ 50 MGD
Turb
idity
(NTU
)
Turb
idity
(NTU
)Fl
ow (M
GD
)
Flow
(MG
D)
Date Date
Data
Model Input
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Influent Turbidity Load
Cumulative Influent Turbidity Load
Catskill Aqueduct Delaware Aqueduct
Kensico Results - ComparisonCatskill Aqueduct Input Chosen for Comparison: 30 NTU @ 50 MGD
Turb
idity
Loa
d (M
GD
*NTU
)
Turb
idity
Loa
d (M
GD
*NTU
)
Date Date
Turb
idity
Loa
d (M
GD
*NTU
)
Turb
idity
Loa
d (M
GD
*NTU
)
Data
Model Input
38
Effluent Turbidity
Catskill Aqueduct Delaware Aqueduct
Kensico Results - ComparisonCatskill Aqueduct Input Chosen for Comparison: 30 NTU @ 50 MGD
Turb
idity
(NTU
)
Turb
idity
(NTU
)
Date Date
Data
Model Output
39
Conclusions
• Uncertainties in modeling system results can arise from initial conditions, forecast inputs and model errors.
• DEP has developed an extensive suite of water quality and water system models to analyze turbidity transport within the Catskill System Reservoirs.
• DEP’s water quality models have been effectively used to help minimize turbidity within Kensico Reservoir.
• Model output uncertainty tends to increase as the length of the model run increases.
• Tracing simulation results by comparison with measured data can indicate:
• when model output no longer applies• when forecast may need to be redone• areas of improvement for the modeling system .