Truckee River Water Quality Standards Review

1. Truckee River Water Quality Standards Review Public Meeting: March 3, 2014

2. 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

3. Overview of Water Quality Standards Review Process

4. 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

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

6. 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

7. Documentation of WQS Review • All relevant reports and presentations available on TRIG (Truckee River Information Gateway) http://truckeeriverinfo.org/tmdl

8. Review of Water Quality Models

9. Peer reviewed, public domain Predicts watershed flow and pollutant loads based on land use meteorological conditions water management watershed improvements WARMF: Watershed Model • 125 catchments (subwatersheds) • Time step = 1 day

10. 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

11. Model Linkage: Model Calibration Meteorology, Land Use, TMWRF Effluent and Re-use Historical Reservoir Releases, Diversions WARMF Historical Diversions Tributary Flows, Nonpoint Sources TRHSPF In-stream Water Quality TMWRF Effluent Compare with observed data

12. 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)

13. Review of Approach for Technical Analysis

14. 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 Sunlight Temperature Flow Dissolved Oxygen Aeration Nutrients (N&P) Organic Matter Algae

15. Model Linkage: WQS Analysis Demands, Water Operations, In-stream Flow Targets Meteorology, Land Use, TMWRF Effluent and Re-use Reservoir Releases, Diversions WARMF Flow Management Model Diversions Tributary Flows, Nonpoint Sources TRHSPF In-stream Water Quality TMWRF Effluent Evaluate water quality response

16. Conceptual Plot of Model Results

17. 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

18. 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

19. 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”

20. 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)

21. Flow Regimes for Water Quality Standards Modeling

22. Set of Simulations

23. Spatial Aggregation for WQS Modeling

24. 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 X days violated 365 days/yr Reviewing attainment as“% of days” is more conservative approach

25. Final Model Simulation Results

26. Final Results Total P10th Percentile Flow: Reach Averaged % of Days % of Hours TN = 0.75 TN = 0.75

27. Final Results Ortho-P10th Percentile Flow: Reach Averaged % of Days % of Hours TN = 0.75 TN = 0.75

28. Final Results Total Nitrogen10th Percentile Flow: Reach Averaged % of Days % of Hours

29. Longitudinal Plot: Low Flow Year TP = 0.05 mg/L OP = 0.05 mg/L

30. Final Results Total P50th Percentile Flow: Reach Averaged % of Days % of Hours TN = 0.75 TN = 0.75

31. Final Results Ortho P50th Percentile Flow: Reach Averaged % of Days % of Hours TN = 0.75 TN = 0.75

32. Final Results Total N50th Percentile Flow: Reach Averaged % of Days % of Hours

33. Longitudinal Plot: Average Flow Year TP = 0.05 mg/L OP = 0.05 mg/L

34. 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

35. Summary of DO Compliance (Percent of Days) * 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).

36. Other Considerations

37. Integrated Flow: Reached Averaged • % violations in Reach 4 (PLPT) much lower when integrating over all flows than for only the low flow year

38. Climate Sensitivity Simulation Low Flow Average Flow Modest increase in percent DO violations with increased air and water temperature

39. 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

40. Reach Geometry Index Marble Bluff Dam (343) Tracy (315) Vista (304) Below Derby Dam (320)

41. Observations

42. 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

43. 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

44. 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

47. 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 TRIG

48. Next Steps

49. 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

50. 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