Focus Group Meeting: August 28, 2013

Truckee River Water Quality Standards Review

Recall: Technical Decision Points for Focus Group Input• WQ models: Review Model Confirmation Report and confirm

that model calibration is complete and satisfactory (Jul/Aug)• WQS modeling process

– General approach for analysis (Jul/Aug)– Selection flow years/conditions for analysis (Aug)– Analysis of model results (spatial aggregations, critical reach, critical

season/month) (Aug) – Speciation of Phosphorus WQS: Ortho-P vs. TP (Aug/Sep)– TN WQS: evaluation of both single value max and annual ave. WQS

(Aug/Sep)• Results of WQS model runs (Aug/Oct)• Technical Rationale for WQS revision (Oct/Jan)

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Overview of Topics for Discussion• Comments on model calibration/confirmation• Proposed approach for WQS modeling

– General approach– Flow regimes– Analysis and interpretation of model results

• Preliminary results of WQS model runs

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Feedback on Model Confirmation

Summary of Focus Group Comments

• General Comment: “Is this model being designed to predict future water quality issues or what is it used for? I don’t understand.”– Currently used to assess alternate water quality

standards

• Additional Feedback?

Overview of General Approach for WQS Modeling

Development of Technical Rationale

Use of Models for WQS Review

• Provide linkage between nutrient concentrations in the Truckee River and resulting dissolved oxygen levels

• Account for other factors (flow, temperature, light, organic matter, aeration)

• Understand river water quality response (dissolved oxygen) to ranges of nutrient concentrations under range of flow conditions

• Establish site-specific nutrient criteria

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Dissolved Oxygen

Sunlight

Flow

Algae

AerationNutrients (N&P)

Temperature

Organic Matter

Shifting from Model Calibration to Application• Calibration/Confirmation

– Generate confidence model is capable of accurately simulating historical river conditions

• Model application– Predict water quality response under hypothetical

scenarios (e.g., potential WQS levels)

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Model Linkage: Model Calibration

WARMF

TRHSPF

Historical Reservoir Releases, Diversions

Historical Diversions

Tributary Flows, Nonpoint Sources

In-stream Water Quality

Meteorology, Land Use, TMWRF Effluent and Re-use

TMWRF Effluent

Compare with observed data

Model Linkage: WQS Analysis

WARMF

TRHSPF

TROM(flow management

model)

Reservoir Releases, Diversions

Diversions Tributary Flows, Nonpoint Sources

In-stream Water Quality

Demands, Water Operations, In-stream Flow Targets Meteorology, Land Use, TMWRF

Effluent and Re-use

TMWRF Effluent

Evaluate water quality response

Assumptions for Model Application• Flow management model provides model inputs

reflective of historical climate/hydrology under selected river operations:– Reservoir releases– Diversions– TMWRF discharge flows

• Climate – consistent with selected representative year

• Land use / land cover – updated layer circa 2006

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WQS Modeling Steps

• Select flow management model• Establish representative flow period(s)• Construct / run a set of scenario runs

– Link flow management model with WQ models– Vary N and P concentrations, examine DO response– Use visualization tools to view / report results

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Flow Regimes

Development of Technical Rationale

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Why Flow Regime is Important• Truckee River water quality relates to flow

– Managed flow conditions– Highly variable flow conditions year to year

• WQS are set to protect Beneficial Uses throughout the expected range of flows (except during extreme low/high flows)

• Low flow periods and low flow locations– Highest potential for algal growth and depressed DO in rivers

• WQS don’t apply if flows are too low– NAC 445A.121(8) – “The specified standards are not considered

violated when the natural conditions of the receiving water are outside the established limits, including periods of extreme high or low flows”

How is Low Flow Normally Set• Not defined in regulations• 7Q10 Statistics typically used

– Low 7-day flows expected to occur once every 10 years– Drawbacks with highly regulated system such as Truckee

• WQS Review– Can’t rely on historical flows; need to use “best

professional judgment” to define alternative approach– Based on TROM simulations of 100 years of operations– NDEP recommends using two flow conditions for analysis

• ~10th lowest year from the simulations• ~50th lowest (average) year from the simulations

Use of TROM Model Output to Select Low Flow Year

• 100 years of predicted flows: 1901 - 2000• TROM Scenarios:

– Future No Action: 2033 TMWA Demand, Historic Operations, build out of M&I

– Future TROA: 2033 TMWA Demand, TROA Operations– Current: 2002 TMWA Demand, Historic Operations

Assumptions for TROM Scenarios

Scenario Time Frame

Reservoir Operations

TMWA Demand

TMWA Irrigation

Rights Acquired

Truckee Meadows

Agricultural Demand

TMWRF Discharge and

Reuse

Newlands Project

Demands

Lower Truckee River Demand (Direct Use and

Instream Demand)

Current (EIS/EIR)

2002 Current operations

83,140 AF

57,170 AF 40,770 AF 26.53 MGD, Reuse: 0.24 MGD

Carson: 275,720,Truckee: 18,520,Fernley M&I: 0

Direct: 12,040 AF Instream: 0 AF

Future - No Action (EIS/EIR)

2033 Current operations

119,000 AF

83,030 AF 21,500 AF 40.01 MGD, Reuse: 9.7 MGD

Carson: 268,870,Truckee: 0,Fernley M&I: 6,800

Direct: 17,900 AF Instream: 16,380 AF

Future –TROA (EIS/EIR)

2033 TROA – store Credit Water

119,000 AF

93,550 AF 4,860 AF 40.01 MGD,Reuse: 9.7 MGD

Carson: 268,870,Truckee: 0,Fernley M&I: 6,800

Direct: 17,900 AF Instream: 16,380 AF

Future No Action (FNA) is most appropriate scenario

Selection of Representative Flow Conditions

• NDEP developed a process for derivation of “target flows” based on TROM FNA output (NDEP Memorandum 12/28/2011)

• Two representative flow regimes selected to date– Low Flow (10th percentile)– Average Flow (50th percentile)

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Selection of 10th Percentile Flow Year: 1977

• 1977 better match than 1994 or 1988

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• 1994 better match than 1988 or 1977

Conducted preliminary WQS simulations conducted for 1977, 1994, and 1988

Adjustment for 10th Percentile Year

• Considered options for better representation of 10th percentile flow year– Choose single year most representative of critical flows above and

below Derby Dam (e.g., 1977)

– Use a hybrid of multiple years• e.g., upper river 1977, lower river 1994

– Develop a separate synthetic year that matches 10th percentile targets

• Decided to keep 1977 FNA intact– Derived from the TROM FNA years closest to target flows

– Retains link between flow regime and historical climate data

– Only adjusted flows at Derby Dam for 1977 to bring closer to target values

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1977 FNA Comparison of TROM, 10th percentile flows, and TRHSPF

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Selection of 50th Percentile Year: 1985

• Investigated several candidate (recent) years based on TROM Future No Action (FNA) flows: 1973, 1985, 1987, 1993, 2000.

• 50%-percentile reference flows (diamonds) generated NDEP method

• Proceeded with using 1985 (FNA) – no additional adjustments

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1985 FNA Comparison of TROM, 50th percentile flows, and TRHSPF

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Analysis and Interpretation of Model Results

Development of Technical Rationale

General Approach: Iterative TRHSPF WQS Simulations• Representative flow year (TROM output)• TRHSPF run iteratively with different concentrations of

TN/TP/Ortho-P– Adjust N and P loads into river (increase or decrease) to match a range of

annual average river concentrations – Concentrations vary temporally but hit target WQS on an annual average

basis

• Locations with adjustments:– East McCarran (upstream model boundary)– Segments with incoming loads (North Truckee Dr., Steamboat Cr., TMWRF)

• Evaluate resulting attainment of DO WQS

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Iterative Runs: Adjust Instream Concentrations = Specified WQS

Derek to provide WinModel screendumps illustrating how a time series of concentration was adjusted to as part of an iterative run

Target TN=0.75 mg/l, Reach 301 (E. McCarran)Blue = BaselineGreen = WQS Run Increased load to meet a target concentration

Sets of Simulations Orthophosphate (mg/L)

Total

Nitrogen

(mg/L)

0.030 0.040 0.050

PLPT std0.075 0.100

0.55 x0.65 x0.75

NDEP/PLPT std x x x x x0.85 x1.00 x

Total Phosphorus (mg/L)

Total Nitrogen

(mg/L)

0.030 0.040 0.050

NDEP std0.075 0.100 0.125

0.55 x 0.65 x 0.75

NDEP/PLPT std x x x x x x0.85 x 1.00 x

Conceptual Plot of Model Results

Possible Nutrient WQS

% o

f tim

e D

O W

QS

is v

iola

ted

(Based on representative flow condition)

Relationship between Nutrient Concentrations and DO WQS Attainment

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Conceptual Plot of Model Results

Possible Nutrient WQS

0.04 0.060.05

% o

f tim

e D

O W

QS

is v

iola

ted

0.0

5.0

10.0

Based on representative flow condition

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Translate DO Concentrations to Compliance

• Model simulates DO Concentrations for every hour at every model segment

• Need to translate to compliance with DO WQS

DO Compliance Considerations

• Highly dependent on the spatial and temporal scale upon which the DO exceedance percentages are calculated

• Next steps: – Evaluate the results at different spatial and

temporal scales – Make an educated determination as to what is

appropriate

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Options for Calculating Percent Violation of DO WQS

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% 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

X days violated365 days/yr

Reviewing attainment as “% of days” is more

conservative approach

Complexity of WQS Modeling Process• Models generate a lot of information

– 38 simulations (19 for each flow regime)– 43 river segments, 8760 hours per year…– 14,313,840 dissolved oxygen modeled data points

• Need to aggregate/distill model output for efficient decision making

• Working Group has been testing and revising methodology for last two years

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Considered Various Post-Processing Options• Spatial Aggregation

– Coarse aggregation (Above Derby, Below Derby)– NDEP Control Point Reaches– Most critical reaches (individual segments)

• Temporal Aggregation– Annual aggregation – Critical season: June-September– Critical month

• Tested options with preliminary WQS simulations

Annual Critical Season (June-September)

Critical Month (e.g., June & September)

Above Derby Dam/ Below Derby Dam X X X

NDEP control point reaches X X X

Most Critical Reaches X X X

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Approach for Post-processing and Aggregation

• Percent of days and percent of hours• Annual and critical season (June – Sep)• Four aggregated reaches and individual critical

reaches• TN range evaluated at two phosphorus levels

– Ortho-P at 0.05 mg/L (PLPT WQS)– Total P at 0.05 mg/L (current NDEP WQS)

• Develop select additional plots/tables– Magnitude of violation

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Spatial Aggregation for WQS Modeling

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WQS Post-Processing and Aggregation of Results

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NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

NDEP Reaches (4)

Critical Reaches (4)

Flow Regime Spatial AggregationTemporal AggregationCompliance MethodConstituent

TP

OP

TN

10% Flow (1977 FNA)

Percent of Days

Percent of Time

Percent of Days

Percent of Time

Percent of Days

Percent of Time

Critical Season (Jun-Sep)

Annual Aggregation

Critical Season (Jun-Sep)

Annual Aggregation

Critical Season (Jun-Sep)

Annual Aggregation

Critical Season (Jun-Sep)

Annual Aggregation

Critical Season (Jun-Sep)

Annual Aggregation

Critical Season (Jun-Sep)

Annual Aggregation

Preliminary WQS Modeling Results

Preliminary Low Flow Year Results

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Preliminary Average Flow Year Results

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Next Steps

• Finalization of model confirmation report• Focus Group comments and feedback (Sept 13th):

– Technical approach• Finalization of WQS model runs/output interpretation• Development of Technical Rationale Report• Upcoming Focus Group Workshops (City of Fernley)

– Sep 27, 2013 (F): 9 AM – 12 PM - modeling results– Oct 16, 2013 (W): 9 AM – 12 PM – Jan 15, 2014 (W): 9 AM – 12 PM – Additional Stakeholder / Focus Group meetings TBD in 2014

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