Making the NHD Flow:

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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
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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

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NWPCAM

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

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Study Area
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Routing With the VAAs
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Hydrologic Sequence Numbers
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Routing With the VAAs
The Reach File Routing Algorithm   Accumulating/M
odeling some Value DIM VAL(10)   Sort Reach
File in SEQNO Order The Actual Routing
Algorithm Loop on Reaches If SFLAG1 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 Jgt0 and J (LEV-1) then
VAL(J) VAL(J) VAL(LEV) VAL(LEV)
0 Endif End Loop  
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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

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Drainage Area Estimates
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Drainage Area Estimates
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Drainage Area Estimates
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USGS Gaging Stations
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Drainage Area QA Step 1
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Drainage Area QA Step 2
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Drainage Area QA Log-Log
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NWPCAM/RF3 Drainage Area QA Similar Results
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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

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Flow QA Linear
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Flow QA Log-Log
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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

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RF1 Vs. NHD Velocities
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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

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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

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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