Water Quality Model Updates to Support Truckee River Nutrient WQS and TMDL Reviews

1. Water Quality Model Updates to Support Truckee River Nutrient WQS and TMDL Reviews December 14, 2011 Laura Weintraub

2. Review of Model Update Approach • Goal: develop best possible tools given reasonable time, information, and funding • Due diligence to ensure models work well for recent time period • Model update steps: • Extend models to run through 12/2008 • Document changes to models and databases, results of model confirmation • Disseminate information to the focus stakeholder group • Original calibration reports (Systech 2007, LimnoTech 2008) • Model update report (LimnoTech November 28, 2011)

3. Model Linkage – Observed Conditions Climate Soil Types WWTPs Pollutant Land Use Loads Watershed Water Quality Water Management Practices Model Model Quality Water Reservoir Releases Quantity WARMF TRHSPF

4. WARMF Updates

5. Recent WARMF Enhancements (post-calibration) • Model Version Update (October, 2008) • Received from Systech • Finer spatial resolution, general database update and recalibration • Temperature improvements (Systech) • Bedrock heat transfer, river ice formation, warming from river friction

6. WARMF Database Updates through 2008

7. Limited WARMF Model Changes • Adjusted initial soil moisture reflects start of new time period • Set breakpoint for updated land use / land cover • Pre-2002 simulations: old GIS layer circa late 1990’s • Post-2002: updated GIS layer circa 2006 • Adjusted organic carbon and nutrient soil concentrations post-2002 • Rapid land use change; model does not completely capture impacts with just surface loading changes • Consistent with findings of Chalk Creek study (JBR, 2010) • Directly specified reservoir releases (historical data) rather than modeling reservoir operations

8. Flow at Reno/Sparks

9. Flow at North Truckee Drain

10. Flow at Steamboat Creek

11. Total Nitrogen at Reno/Sparks

12. Total Nitrogen at North Truckee Drain

13. Total Nitrogen at Steamboat Creek

14. Total Phosphorus at Reno/Sparks

15. Total Phosphorus at North Truckee Drain

16. Total Phosphorus at Steamboat Creek

17. Summary of WARMF Results • Flow • Strong model performance at Truckee River at Sparks (upstream boundary for TRHPSF): r2 = 0.87 • Moderate performance at North Truckee Drain and Steamboat Creek • Day to day variability is small compared to Truckee River • Although variability not captured well, model accurately describes average flows • Nutrients • Model predictions fall within range of uncertainty of observed data for large majority of years • Results consistent with previous calibration

18. Known Limitations in WARMF Performance • Snow melt peaks under-predicted during wettest years • Does not impact critical low flow periods • Summer residential irrigation not captured (potable / reuse water) • Little impact to summer flows in Truckee River downstream of confluence with Steamboat Creek and NTD • Remaining underprediction of spring streamflow temperatures • Sensitivity analysis showed only minor changes to DO with higher temperatures during this non-critical late winter / early spring period Above limitations do not preclude the use of the model for intended need

19. TRHSPF Updates

20. Recent TRHSPF Enhancements (post-calibration) • Organic labile nutrient representation • New state variables for org. labile nitrogen and organic labile phosphorus • No longer derived indirectly from BOD and phytoplankton stoichiometry • Directly accounts for settling and decay • TRHSPF linkage with WARMF • Upstream and tributary boundary conditions from WARMF • Provides capability to evaluate Truckee River response to changes in watershed activity • Implemented discrete segment for Gilpin Spill bypass • Model accounts for potentially “depleted” segment between Derby Dam and Gilpin Spill return

21. TRHSPF Database Updates through 2008

22. Limited TRSHPF Model Changes • Flow balance corrections • Truckee Canal and Gilpin Spill flow based on USGS gages • Known limitations in gage accuracy • Truckee Canal flows adjusted to prevent negative Truckee River flows for periods of obvious mismatch – “error” sent down the canal • Addressed occasional model instability when model segment flow dropped to “zero” • Applied minimal “floor” segment volume (100 ft3) • Holds back minimal flow in segment during unstable timestep • Result: adjustment to flow out of segment < 0.05 cfs

23. TRHSPF Flow Results

24. TRHSPF Flow Results

25. TRHSPF Total Nitrogen Results

26. TRHSPF Total Nitrogen Results

27. TRHSPF Total Phosphorus Results

28. TRHSPF Total Phosphorus Results

34. Prediction of Annual Nutrient Loads • Noted limitations in WARMF-predicted snow melt peaks • Important to adequately predict total annual loads from Truckee River to downstream water bodies • Compared with load estimations from data • Results within range of uncertainty of LOADEST results for majority of years

35. Summary of TRHSPF Results • Flow • R2 ranges between 0.85 to 0.88 for all stations • Rating of “very good” • Nutrients • Model predictions fall within range of uncertainty of observed data for large majority of years • Observed error statistics consistent with original calibration • Dissolved Oxygen • Time series plots and observed error statistics consistent with original calibration

36. Summary of Model Update • Confirmation of WARMF and TRHSPF for 2000-2008 period • Model updated to reflect rapid regional growth through 2006 • Both models are ready for use to support the third-party WQS and TMDL review efforts • Third-parties welcome comments and questions from Focus Stakeholder group

37. Next Technical Steps in WQS Review Process • Solicit feedback from stakeholder group on modeling tools • Submit comments by January 4, 2012 • Construct / run a set of scenario runs • Establish representative low flow • Link flow management model with WQ models • Vary N and P concentrations  DO response • Document any recommendations for revised WQS • Submit report to NDEP for WQS Review

38. Questions?

39. Extra slides

40. Model Database Updates: WARMF Land Use / Land Cover • Old Land Use / Land Cover (LULC) data reflective of late 1990’s • Rapid growth and development through 2006 • New LULC reflective of recent growth • Combination of several datasets • 2006 National Land Cover Dataset (NLCD) – underlying base layer • 2010 Washoe County / Truckee Meadows Regional Planning Agency – developed parcel data supersedes NLCD data • Site-specific additions based on “parks” layer /Google Earth: ski resorts, golf courses, parks, animal feeding operation

42. Late 1990’s currently in WARMF

43. New 2006/2007 layer for import to WARMF (increased development)

44. TRHSPF Modifications for Gilpin Spill • Truckee Canal return flow 7.5 miles downstream of Derby Dam • Allows for fine tuning of TCID diversions and safety control to return water to river quickly

45. Gilpin Spill in TRHPSF • Return flow at Gilpin Spill is ungaged • Typically 40-50 cfs is returned, capacity of 2700 cfs • 7.5 Mile Reach between Derby Dam and Gilpin Spill • Historically as low as 3 cfs • Recent USGS flows higher flow conditions • TRHSPF previously only diverted “Net” Truckee Canal diversion flow (no bypass from Gilpin Spill) • No additional depletion in stretch just below Derby • Need to accommodate possible depleted conditions in WQS/TMDL analysis

46. Gilpin Spill in TRHSPF “Improved” • Model Gilpin Spill explicitly • Calculate diversion and return based on USGS flows • Add a model segment to represent Gilpin Spill “bypass” • Assume water quality in the return is the same as Derby Dam TCIDtot= TR near Tracy – TR below Derby TCIDnet = Truckee Canal near Wadworth Gilpin Spill = TCIDtot - TCIDnet