Transcript Slide 1

Truckee River Water Quality
Standards Review
Focus Group Meeting: September 27, 2013
Overview of Topics for Discussion
• Feedback from previous workshop?
• Review of flow regime development
– Adjustment to 10th percentile flow regime
• Preliminary WQ results
• Interpretation of Results
– Integration of results over range of flows
• Preliminary climate change sensitivity runs
• Next steps
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Feedback from Previous Workshop
Topics for Comment from August 2013
Focus Group Meeting
• Approach for applying WARMF and TRHSPF to
evaluate potential changes to the Truckee River
Nutrient Water Quality standards
• Approach for establishing a flow regime based on
TROM Future No Action scenario
• Approach for analysis and interpretation of model
results
• Any overarching concerns regarding the water
quality standards review process?
Review of Flow Regime
Development
Selection of Representative Flow
Conditions
• Derived “target flows” based on TROM Future
No Action output
• Two representative flow regimes selected to
date
– Low Flow (10th percentile)
– Average Flow (50th percentile)
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1977 FNA Comparison of TROM,
10th percentile flows, and TRHSPF
ONLY Adjusted
at TCID
• Only adjusted summer period for lower river
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Refining 10th Percentile Flow
Regime Closer to Target
• Preliminary runs performed with only minor
adjustment to 1977 FNA (at Derby Dam)
• Working Group recommended further
adjustment for 1977 above Derby Dam
• Final results with adjusted flows are
“in process”
• Single test run completed
– Biggest change in Reach 1
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1977 FNA Comparison of TROM,
10th percentile flows, and TRHSPF
Adjusted at
Sparks Jul - Sep
ONLY Adjusted
Adjusted at TCID
at TCID
• Adjusted at WARMF-TRHSPF interface
– July, August decreased flow
– September increased flow
• Adjusted summer period for lower river
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Single Test Run with Adjusted
10th Percentile Low Flow
Ortho-P
TN
Proceeding with running adjusted 10th percentile flow for
full suite of constituent concentrations
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1985 FNA Comparison of TROM,
50th percentile flows, and TRHSPF
• No additional adjustment
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Preliminary Results of 10th
Percentile Low Flow Condition
(Does not include adjusted flow regime)
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Set of Simulations
Orthophosphate (mg/L)
Total Nitrogen (mg/L)
0.030
0.040
0.65
NDEP/PLPT std
x
PLPT std
x
x
x
x
x
0.55
0.75
0.050
x
0.85
1.00
0.075
0.100
x
x
Total Phosphorus (mg/L)
Total Nitrogen (mg/L)
0.030
0.040
0.55
0.65
0.75
NDEP/PLPT std
0.85
1.00
x
x
0.050
NDEP std
x
x
x
x
x
0.075
0.100
0.125
x
x
x
Options for Calculating Percent
Violation of DO WQS
% of Hours: attainment is aggregation of all
hours that have violated WQS
X hours violated
8760 hours/yr
% of Days: if 1+ hours violate WQS on a given
day, that day is not in attainment
Reviewing attainment as
“% of days” is more
conservative approach
X days violated
365 days/yr
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Spatial Aggregation for WQS Modeling
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Preliminary Results Total P
10th Percentile Flow: Reach Averaged
% of Days
TN = 0.75
% of Hours
TN = 0.75
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Preliminary Results Ortho-P
10th Percentile Flow: Reach Averaged
% of Days
TN = 0.75
% of Hours
TN = 0.75
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Preliminary Results Total Nitrogen
10th Percentile Flow: Reach Averaged
% of Days
% of Hours
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Preliminary Results: Longitudinal Plots
TN = 0.75 mg/L, OP = 0.05 mg/L
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Preliminary Results Total P
50th Percentile Flow: Reach Averaged
% of Days
TN = 0.75
% of Hours
TN = 0.75
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Preliminary Results Ortho P
50th Percentile Flow: Reach Averaged
% of Days
TN = 0.75
% of Hours
TN = 0.75
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Preliminary Results Total N
50th Percentile Flow: Reach Averaged
% of Days
% of Hours
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Preliminary Results: Longitudinal Plots
TN = 0.75 mg/L, OP = 0.05 mg/L
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Preliminary Observations
• Reaches 1, 2, 3 show low level of DO violation
• Reach 4 is most critical at 10th percentile flow
– Sensitive to the phosphorus concentration
– Not sensitive to the TN concentration
– No violations for 50th percentile flows
• Need further investigation of Reach 4
response
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Integration of Results Over Full Flow
Regime
• Working Group discussed potential merit of running
a 90th percentile (high flow) regime
• Could consider an “integration” of DO violations
across all flow regimes
• Spreadsheet calculation based on preliminary results
• 90th percentile year not simulated
– Conservative assumption: high flow violations same as
average year
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Integration Over Flow Regimes:
Compare Target Flows
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Comparison of 10th and 50th Flow
Regime Results: Total P
50th Percentile Flow
10th Percentile Flow
TN = 0.75
TN = 0.75
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Preliminary Climate Change
Scenario
• Identified by Focus Group as important consideration for
sensitivity analysis
• Focus only on temperature increase
– Given highly managed system, reservoir management could
override climate change influences in upper watershed
– Climate models predict wide variation in precipitation changes
• General approach for sensitivity runs
–
–
–
–
Only adjust TRHSPF air temperature inputs – air water exchange
Apply a 1° F air temperature increase across entire year
Present the results on a "per degree" basis
Although linear response not expected, reasonable first step
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Basis for 1° F Temperature Increase
• USBR Truckee River Basin Study (2012-2014)
– Evaluate range of potential changes in water demands due
growing population
– Compare demands to existing supply under potential
future uncertainties, including climate change
• Will include use of climate model projections
Approximate 1° F
increase over 20 years
SOURCE: USBR, 2013. Truckee Basin Study, Technical Advisory Group Water Supply Workshop, June 24, 2013
http://www.usbr.gov/mp/TBStudy/
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TP Climate Sensitivity Example:
10th Percentile Flow (TN 0.75 / TP 0.05)
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Geomorphology Considerations
• Potential relationship between channel geometry
and most critical segments
• Mapped selected parameters for each model
segment
– Reach slope
– Water depth (summer average; 10th percentile year)
– Water velocity (summer average; 10th percentile year)
• Developed an “indicator” of segment-specific
diurnal swing
– Calculated for two-segment average to account for
influence by the diurnal in the prior segment
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Justification for Indicator
• Violations are caused primarily by the magnitude of the
diurnal swing
• Diurnal swing at steady state directly proportional to:
gross plant productivity (g O2/m3/day) / [reaeration rate]
• Gross plant productivity =
areal productivity (g O2/m2/day) / [water depth]
• Reaeration proportional to:
[velocity * slope]
• Diurnal swing =
areal productivity / [depth * velocity * slope]
• With similar periphyton productivity across segments,
[depth * velocity * slope] should be a good indicator of
segment-specific diurnal
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Visually Determined “Bins” for
Mapping Parameters
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Average Depth (Summer Mean)
Marble Bluff
Dam (343)
Tracy (315)
Vista (304)
Below Derby
Dam (320)
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Channel Slope
Marble Bluff
Dam (343)
Tracy (315)
Vista (304)
Below Derby
Dam (320)
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Average Velocity (Summer Mean)
Marble Bluff
Dam (343)
Tracy (315)
Vista (304)
Below Derby
Dam (320)
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Reach Geometry Index
Marble Bluff
Dam (343)
Tracy (315)
Vista (304)
Below Derby
Dam (320)
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Next Steps
• Focus Group comments / feedback:
– Technical approach
• Finalization of WQS model runs/output
interpretation
– Finalize “adjusted” 10th percentile flow runs with all
constituent concentrations
– Climate sensitivity simulations
• Development of Technical Rationale Report
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Upcoming Focus Group Workshops
• Early Nov, 2013 (TBD) *NEW DATE*
– Final modeling results
• Jan 15, 2014 (W)
– Technical Rationale document
• Additional Stakeholder / Focus Group
meetings TBD in 2014
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