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Making the NHD Flow: Adding Hydrology to the Hydrography By Tim Bondelid – RTI International

Making the NHD Flow: Adding Hydrology to the Hydrography By Tim Bondelid – RTI International Jeanne Game – RTI International Cindy McKay – Horizon Systems Sponsored By USEPA Office of Water. Project Objectives.

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Making the NHD Flow: Adding Hydrology to the Hydrography By Tim Bondelid – RTI International

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  1. Making the NHD Flow: Adding Hydrology to the Hydrography By Tim Bondelid – RTI International Jeanne Game – RTI International Cindy McKay – Horizon Systems Sponsored By USEPA Office of Water

  2. Project Objectives • Pilot Study to develop drainage area, mean annual flow, and velocity estimates for NHD • Apply simplified techniques originally developed for the National Water Pollution Control Assessment Model (NWPCAM) • Use the Pilot as a test application of the NHD VAAs • QA the results using USGS gaging stations and RF1 velocities

  3. NWPCAM • Acknowledgements: EPA OW, NCEE, OPEI • A national-scale modeling system for policy analysis • RF3-based with VAA’s • Large ORACLE system • Several models are integrated into the system • Includes the hydrologic methods shown in this presentation

  4. Study Area

  5. Routing With the VAAs

  6. Hydrologic Sequence Numbers

  7. Routing With the VAAs The Reach File Routing Algorithm: Accumulating/Modeling some “Value”: DIM VAL(10) Sort Reach File in SEQNO Order **** The Actual Routing Algorithm: **** Loop on Reaches: If SFLAG=1 then VAL(LEV) = 0 ***Reach-specific Value or Modeling here *** VAL(LEV) = VAL(LEV) + RCHVALUE ***Put Accumulated Value into Reach Table*** RCH!VALUE = VAL(LEV) ***Check for end of Stream Level Path*** If J>0 and J = (LEV-1) then VAL(J) = VAL(J) + VAL(LEV) VAL(LEV) = 0 Endif End Loop

  8. Drainage Area Estimates • Associate 1 sq. km. AVHRR grids with the nearest Drain • Provides an estimate of incremental drainage area by Drain • Sum up total drainage areas using VAA routing algorithm • QA using USGS gaging station drainage areas: two steps

  9. Drainage Area Estimates

  10. Drainage Area Estimates

  11. Drainage Area Estimates

  12. USGS Gaging Stations

  13. Drainage Area QA: Step 1

  14. Drainage Area QA: Step 2

  15. Drainage Area QA: Log-Log

  16. NWPCAM/RF3 Drainage Area QA: Similar Results

  17. Flow Estimates • Estimate average annual unit runoff by HUC • Apply distance-weighted unit runoff using NCD gages; simplified “zone of influence” • QA Using USGS runoff isopleth map • Compute incremental Drain runoff – multiply incremental drainage area times unit runoff • Route and accumulate incremental flows to estimate mean annual flow by Drain • QA by comparing to USGS gage mean annual flows

  18. Flow QA: Linear

  19. Flow QA: Log-Log

  20. Velocity Estimates • Use “No Slope” Method of Jobson • Compare to RF1 velocities • Does not measure accuracy • Provides an order-of-magnitude cross-check • Need time-of-travel studies to test accuracy • Could possibly be enhanced with Drain slope estimates • First steps taken to test this

  21. RF1 Vs. NHD Velocities

  22. Advantages Of This Method • Uses simple yet effective methods for bringing key hydrologic attributes into the NHD • Can be developed quickly for the national NHD • Linkages to land cover can bring in NPS loading estimates for large-scale water quality modeling • The VAAs combined with these hydrologic attributes provides a time-tested modeling framework

  23. Conclusions • The simplified methods for estimating NHD hydrologic parameters worked quite well • This Pilot Study validated the NHD VAAs as an efficient and effective application tool • The performance of the simplified methods is comparable to the national-scale results from NWPCAM • Many of the databases and tools are now developed for application in other areas

  24. Recommendations • Repeat the pilot application in other areas • Compare with other NHD hydrologic pilots • Test in arid areas • Compare the simplified velocity estimation techniques to site-specific time-of-travel studies • Do a cost-benefit evaluation of the various NHD hydrologic methods under development • National-scale application to get first-order hydrology estimates into the NHD

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