Public Meeting: March 3, 2014

Truckee River Water Quality Standards Review

Overview of Topics for Discussion• Welcome and introductions • Review of water quality standards review

process– Background– Water quality models– Approach for analysis– Results and observations

• Next steps

2

Overview of Water Quality Standards Review Process

Background on Review of Truckee River Water Quality Standards (WQS)

• Truckee River standards not reviewed since 1993– Science has progressed significantly

• NDEP encourages review of WQS prior to TMDL development

• Jan 6, 2011 – NDEP announces triennial WQS Review process, solicits input– Feb 22, 2011 – Third Parties submit letter to NDEP

requesting review of Total Phosphorus (TP) and Total Nitrogen (TN) WQS

– Truckee River on NDEP list of priority waters for Triennial Review of Water Quality Standards

Current Numeric Nutrient Criteria

5

Note: Also a NDEP single value max OP std of 0.05 mg/L from Stateline to E. McCarran Blvd.

Key Parties in Process• Third-Parties (City of Reno, City of Sparks, Washoe

County, TMWA)– Leading technical review efforts– WRWC – funding– LimnoTech – technical work

• Working Group (third-parties, NDEP, and US EPA)– Technical guidance and review– NDEP will make recommendations for any changes to water

quality standards • Focus Group – stakeholder input and review• General Public – additional review and feedback

6

Documentation of WQS Review • All relevant reports and presentations available on

TRIG (Truckee River Information Gateway)

http://truckeeriverinfo.org/tmdl

7

Review of Water Quality Models

WARMF: Watershed Model

• 125 catchments (subwatersheds)

• Time step = 1 day

9

• Peer reviewed, public domain

• Predicts watershed flow and pollutant loads based on– land use– meteorological conditions– water management– watershed improvements

TRHSPF: River Water Quality Model• Based on science used for 1994 TMDL• Open code, EPA-supported, peer reviewed• Calibrated and verified, technology transferred• Inputs are flow, watershed loads, point sources• Predicts:

– water quality response of river– nutrients periphyton dissolved oxygen

10

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

2012/2013 Model Extension/Update• Effort to keep models current and build confidence in

models• Extended all databases through 12/31/2011

– Minor refinement of calibration– Several previous shortcomings addressed

• Model performance results “as good as” or “better” compared to prior model update

• Documented results in updated model confirmation report (available on TRIG)

12

Review of Approach for Technical Analysis

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

• Review site-specific nutrient criteria

14

Dissolved Oxygen

Sunlight

Flow

Algae

AerationNutrients (N&P)

Temperature

Organic Matter

Model Linkage: WQS Analysis

WARMF

TRHSPF

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

Conceptual Plot of Model Results

16

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

17

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

18

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

• Highest potential for algal growth and depressed DO during low flows

• 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”

Representative Flow Conditions

• Derived “target flows” based on TROM Future No Action output

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

20

Flow Regimes for Water Quality Standards Modeling

21

Set of Simulations

Spatial Aggregation for WQS Modeling

23

Options for Calculating Percent Violation of DO WQS

24

% 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

Final Model Simulation Results

Final Results Total P10th Percentile Flow: Reach Averaged

26

% of Days % of Hours

TN = 0.75 TN = 0.75

Final Results Ortho-P10th Percentile Flow: Reach Averaged

27

% of Days % of Hours

TN = 0.75 TN = 0.75

Final Results Total Nitrogen10th Percentile Flow: Reach Averaged

28

% of Days % of Hours

Longitudinal Plot: Low Flow Year

29

OP = 0.05 mg/L

TP = 0.05 mg/L

Final Results Total P50th Percentile Flow: Reach Averaged

30

% of Days % of Hours

TN = 0.75 TN = 0.75

Final Results Ortho P50th Percentile Flow: Reach Averaged

31

% of Days % of Hours

TN = 0.75 TN = 0.75

Final Results Total N50th Percentile Flow: Reach Averaged

32

% of Days % of Hours

Longitudinal Plot: Average Flow Year

33

OP = 0.05 mg/L

TP = 0.05 mg/L

Summary of Three Scenarios

• Scenario 1: Current numeric nutrient criteria • Scenario 2: Nitrogen levels at current numeric

TN criteria; phosphorus levels at annual average TP = 0.05 mg/l

• Scenario 3: Nitrogen levels at current numeric TN criteria; phosphorus levels at annual average OP = 0.05 mg/l

34

Summary of DO Compliance (Percent of Days)

35

Location

Low Flow Average Flow

Scenario 1: Existing Criteria

Scenario 2: TP=0.05 mg/L

Scenario 3:OP=0.05 mg/L

Scenario 1: Existing Criteria

Scenario 2: TP=0.05 mg/L

Scenario 3: OP=0.05 mg/L

Aggregated

Reaches

Reach 1 0.27 0.27 0.31 1.9 1.9 1.9

Reach 2 0.05 0.05 0.05 0.39 0.39 0.44

Reach 3 0.17 0.17 0.34 0.0 0.0 0.0

Reach 4 5.5 (5.6) 3.2 5.5 (5.6) 0.0 (0.0) 0.0 0.0 (0.0)

Most Critical Segmen

ts

Vista(within Reach 1) 1.6 1.6 1.9 5.9 5.9 5.9

Tracy (within Reach 2) 1.1 1.1 1.1 3.2 3.2 3.5

Below Derby (within Reach 3) 2.5 2.5 2.5 0.0 0.0 0.0

Marble Bluff Dam (within Reach 4) 23 (23) 11 23 (23) 0.0 (0.0) 0.0 0.0 (0.0)

* The value in parentheses denotes the percent DO violation calculated using a flow-weighted average OP concentration. This is the method of calculation specified for the current OP numeric criteria in the PLPT jurisdiction (Reach 4).

Other Considerations

Integrated Flow: Reached Averaged

37

• % violations in Reach 4 (PLPT) much lower when integrating over all flows than for only the low flow year

Climate Sensitivity Simulation

38

Low Flow Average Flow

Modest increase in percent DO violations with increased air and water temperature

River Geomorphology and Restoration

• Supplementary information included with analysis• Potential relationship between channel geometry and

most critical segments• Developed and mapped “indicator” of potentially

vulnerable regions – Based on depth, velocity, slope

• Mapped restoration activity• Model is a conservative representation of actual river

– TRHSPF parameterized for pre-restoration geometry condition

Reach Geometry Index

40

Vista (304)

Tracy (315)

Marble Bluff Dam (343)

Below Derby Dam (320)

Observations

Summary of Technical Findings

Reaches 1, 2, 3 of the Truckee River• DO criterion violation is low over the entire range of

annual average nutrient concentration examined• With both low and average flow, no sensitivity to

increasing phosphorus concentrations• With low flow, slight sensitivity to increasing TN

concentrations– Does not occur unless the annual average TN concentration is

greater than approximately 0.80 mg/L– Verifies appropriateness of existing TN criterion

Summary of Technical Findings (continued)Reach 4 of the Truckee River• DO criterion violation varies depending on nutrient concentration

and flow regime• For low flow, Truckee River is sensitive to the phosphorus

concentration– No DO criterion violations were calculated for the average flow regime

• For both low and average flow, no sensitivity to TN concentration over the range examined– For the low flow, DO criterion violations ranged from 3% to 6% of days

• For average flow, no DO criterion violations regardless of nutrient concentrations (N and P)

• DO criterion violations sensitive to other factors beyond phosphorus concentration– Flow condition, channel geometry and stream temperature

Closing Thought• If the Nevada phosphorus criterion were changed to be

consistent with the current PLPT criterion, there would be no expected increase in DO violations in the Truckee River under either low flow or average flow conditions compared to conditions under existing standards

44

45

46

WQS Technical Analysis Documented in LimnoTech Report

• Provides NDEP and U.S. EPA with technical information to support their triennial review of the nutrient water quality standards for the Truckee River in Nevada

• Provided to Focus Group for review

• Available on TRIG47

Next Steps

Next Steps in Process

• Any proposed recommendations for changes from the existing nitrogen and phosphorus numeric nutrient criteria will be developed by and documented by NDEP in a rationale document – NDEP report will be available for public comment

• Any proposed changes will need to be approved by the State Environmental Commission and U.S. EPA before becoming effective under the federal Clean Water Act

NDEP Tentative Timeline• 1/17/2014: Draft LimnoTech report on modeling results

• 1/28/2014: NDEP Public Workshop - Relaunch WQS review

• 2/14/2014: Review completed by Focus Group

• 3/1/2014: Final LimnoTech report on modeling results

• 3/3/2014: NDEP Public Workshop - Present LimnoTech Technical Report

• April 2014: NDEP develop rationale/petition for proposed standards changes

• Early May 2014: NDEP Public Workshop – Present Draft Rationale

• 6/30/2014: Final NDEP Rationale/Petition to Legislative Counsel Bureau

• October 2014 (expected): State Environmental Commission hearing

50

Questions?

51