Truckee River Water Quality Standards Review

1. Truckee River Water Quality Standards Review Focus Group Meeting: July 17, 2013

2. Overview of Topics for Discussion • Recap on Water Quality Models to Support WQS Review • Recent updates • Model confirmation report • Overview of general approach for WQS modeling  • Technical decision points • Anticipated schedule and milestones

3. Recap on Water Quality Models to Support WQS Review

4. Intended Use of Models • Explore river water quality response to ranges of point and nonpoint concentrations/loads under range of flow conditions • Model results support review of WQS and TMDL • WQS: establish site-specific response to nutrient concentrations • TMDL: help understand possible balances of point and nonpoint loads which result in DO WQS attainment

5. Model Linkage for Truckee River WQS Analysis Demands, Water Operations, In-stream Flow Targets Meteorology, Land Use, TMWRF Effluent and Re-use Reservoir Releases, Diversions WARMF TROM Diversions Tributary Flows, Nonpoint Sources TRHSPF In-stream Water Quality TMWRF Effluent

6. 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

7. TRHSPF: River Water Quality Model • Based on DSSAMt 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

8. Recap of 2011 Model Extension/Update • Updated both WARMF and TRHSPF • Extended databases through 12/31/2008 • Models reflect rapid regional growth through 2006 • Refined calibration • Model limitations identified in 2011 • Under-prediction of snow melt peaks in wetter years (WARMF) • Under-prediction of flow in Steamboat Creek and North Truckee Drain during summer due to landscape irrigation with potable/reclaimed water (WARMF) • Under-prediction of stream temperature during spring (WARMF) • Non-critical periods for dissolved oxygen • Under-prediction of total nitrogen and total phosphorus • Non-bioavailable organic nutrient component is low

9. Recap of 2011 Model Extension/Update (continued) • Overall Model Performance • Results consistent with original calibration • Model performance still acceptable for more recent time periods • Both models considered ready for use to support the third-party WQS and TMDL review efforts • Reporting • Documented results in Model Confirmation Report (11/28/11) • Presented results to stakeholders in December 2011

10. 2012/2013 Model Extension/Update • Goal: keep models current and build confidence in models • Extended all databases through 12/31/2011 • Climate, diversions, point sources, air quality, reservoir operations, observed flow, observed water quality • QA/QC of diversion input data to ensure consistency between the watershed and river model • Upgraded to WARMF Version 6.5b (released 5/2012) • Minor refinement of calibration • WARMF: Minor soil coefficient and temperature lapse factor adjustments to improve simulation of extreme low-flow conditions and upper watershed snowmelt hydrology • TRHSPF: Slight decrease in rate of organic labile N and P settling

11. Snapshot Summary of Results • Several previous shortcomings addressed • Improved snowmelt and low flow hydrology in upper watershed • Reduced general under-prediction of total nitrogen • Updated and QA/QC’d diversion data across all models • Overall Model Performance • Results “as good as” or “better” for 2000-2008 as compared to prior model update • Results within the range of uncertainty for new years (2009-2011) - 2009 was a challenging/unusual year • Overall, total nutrients are still slightly low • Inorganic nutrients within range of uncertainty • Organic nutrients slightly low • Increasing organic nutrients will not change DO significantly • Documented results in updated model confirmation report

12. WARMF: Flow at Reno/Sparks

13. WARMF: Total Nitrogen at Reno/Sparks 2009 unusual year

14. WARMF: Nitrogen Species at Reno/Sparks

15. WARMF: Total Phosphorus at Reno/Sparks

16. WARMF Model Confirmation Summary • Flow • Extreme low-flow periods and snow melt peaks improved with minor parameter modifications in upper watershed (above Farad) • r2 for the Truckee River at Reno/Sparks improved slightly to 0.89 (considered “very good”) • Nitrogen • Inorganic nitrogen within range of uncertainty • Total nitrogen generally lower than observed • Bias in observed data due to non-detects? • Missing or underestimated organic nitrogen source? • Phosphorus • Annual and long-term total phosphorus and orthophosphate within range of uncertainty • Many observed TP values at Reno/Sparks below PQL

17. TRHSPF: Streamflow at Vista Slight improvement in r2 from previous model confirmation results

18. TRHSPF: Total Nitrogen at Lockwood 2009 unusual year

19. TRHSPF: Total Phosphorus at Lockwood data anomalies?

20. TRHSPF: Dissolved Oxygen(Tracy/Clark: 2002-2005)

21. TRHSPF: Dissolved Oxygen(Tracy/Clark: 2006-2011)

22. TRHSPF Model Confirmation Summary • Flow • r2 ranges between 0.86 to 0.90 for all stations • Rating of “very good” • Nutrients • Model predictions fall within range of uncertainty of observed data for large majority of years (exception is 2009) • Slight under-prediction of TN and TP • Inorganic nutrients are reasonable overall • Inorganic N within the range of uncertainty • Ortho-P slightly over-predicted • Organic nutrients slightly low • Dissolved Oxygen • Model predictions are within the range of the data • Overall model performance is “good”

23. Review of Model Confirmation Report • Confirmation Report available on TRIG July 23, 2013 • Email to Focus Group • Form for written comments on confirmation report (electronic submittal) • Due August 16th, 2013 • Supplementary background material on TRIG • Original calibration reports • Presentations from previous Focus Group meetings • TRIG – Truckee River Info Gateway: • http://truckeeriverinfo.org

24. Overview of General Approach for WQS Modeling Development of Technical Rationale

25. Modeling Approach to Support WQS Review Objective: Identify appropriate site-specific nutrient WQS that when met, would adequately meet DO criteria given a representative flow condition • Identify flow condition(s) • Test range of instream concentrations of nitrogen and phosphorus • Evaluate the extent to which the DO water quality standard will still be met

26. Conceptual Plot of Model Results Relationship between Nutrient Concentrations and DO WQS Attainment % of time DO WQS is violated (Based on representative flow condition) ? Possible Nutrient WQS

27. Conceptual Plot of Model Results 10.0 Based on representative flow condition % of time DO WQS is violated 5.0 ? 0.0 0.04 0.05 0.06 Possible Nutrient WQS

28. General Approach: Iterative TRHSPF WQS Simulations • Representative flow year (TROM output) • Linked WARMF – TRHSPF simulation • WARMF provides “baseline” loads and flows into river • TRHSPF run iteratively with different concentrations of TN/TP/Ortho-P • Adjust N and P loads into river (increase or decrease) to match annual average river concentrations to “proposed” WQS • Locations with adjustments: • East McCarran (upstream model boundary) • Segments with incoming loads (North Truckee Dr., Steamboat Cr., TMWRF) • Evaluate resulting attainment of DO WQS

29. Matrix of Scenarios Tested with 10th Percentile and 50th Percentile Flow Regimes • Concentrations vary temporally but hit target WQS on an annual average basis • Incoming loads are adjusted at upstream boundary (E. McCarran), North Truckee Drain, and Steamboat to hit target WQS

30. Technical Decision Points

31. Technical Decision Points for Focus Group Input • WQ models: Review Model Confirmation Report and confirm that model calibration is complete and satisfactory (Jul) • WQS modeling process • General approach for analysis (Jul) • 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)

32. Anticipated Schedule and Key Milestones

33. Next Steps • Focus Group comments and feedback: • Model Confirmation Report • Technical approach • Working group proceeding with resolution of technical decision points • Continuation of preliminary WQS model runs • Upcoming Focus Group Workshops (City of Fernley) • Aug 28, 2013 (W): 9 AM – 12 PM • Comments on model confirmation report due August 16 • Sep 18, 2013 (W): 9 AM – 12 PM • Oct 16, 2013 (W): 9 AM – 12 PM • Jan 15, 2014 (W): 9 AM – 12 PM • Additional Stakeholder / Focus Group meetings TBD in 2014

34. NDEP Timeline • 12/1/2013: Preliminary Draft LimnoTech report on modeling • 1/1/2014: Review completed by Working Group • 1/15/2014: Draft LimnoTech report on modeling results • 2/15/2014: Review completed by Focus Group • 3/1/2014: Final LimnoTech report on modeling results • 4/1/2014: Draft NDEP Rationale/Petition for proposed standards changes • 5/1/2014: NDEP Workshops – Focus Group, general public • 6/30/2014: Final NDEP Rationale/Petition to LCB