Calculating Hydrologic Parameters for Estimating Surface Water Flow at Ungaged Locations Richard Hoffpauir Water Resources Engineering

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Calculating Hydrologic Parameters for Estimating
Surface Water Flow at Ungaged LocationsRichard
HoffpauirWater Resources Engineering
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Gaged Locations
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Ungaged Locations
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Estimating Flow at Ungaged Locations

• Proportional change in drainage area and average
  upstream parameters

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Linear Relationship Assumed
Gaged
Ungaged
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Other Methods for Estimating Flow at Ungaged
Locations

• Modifying an emperical model calibrated to a
  gaged location (e.g. SCS Curve Number Method)
• Regionalized precipitation-runoff regression
• Hydrologic simulation (e.g. HEC-HMS)

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Why is this important?
Surface water withdrawl permits are not always
granted next to stream gaging stations. Flow
at the permitted location is used to determine
the users withdrawl reliability. Further
complicating the scenario, the permitted volume
of withdrawl affects the flow and reliability
for downstream users.
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1997 Texas Senate Bill 1

• Comprehenisive regional water resources planning
  for future demands and droughts
• Water Availability Modeling (WAM)
• Water Rights Analysis Package (WRAP)

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Application of WRAP

• Flow at ungaged locations is typically modeled
  using parameter ratios.
• Priority based water allocation model
• Existing water management policies can be
  evaluated with historical stream flow data.
• Proposed water withdrawl permits are evaluated
  based on their impact to downstream users.

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WRAP Parameters ArcView Script

• Brad Hudgens
• CRWR Online Report 99-4
• Interface to simplify calculation of upstream
  parameters for a set of control points on a
  stream network

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Objectives of My Project

• Develop GIS datasets for the Brazos River Basin
  (e.g. flow accumulation, stream network, control
  points, CN, precip, etc) and to become proficient
  with the WRAP Parameters ArcView tools.
• Compare hydrologic parameters obtained at 67
  control points to the values submitted to the
  TNRCC as part of the WAM project for the Brazos.

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Datasets Used for this Project

• Grid USGS 1-Degree DEM (1250,000 accuracy)
• Grid U.S. Curve Number
• Grid U.S. Mean Annual Precipitation
• Lines EPA RF3 and NHD Channel Lines (1100,000
  accuracy)
• Points Control Point Locations

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Brazos River Basin

• Los Brazos de Dios
• 46,000 sq. miles
• 36,000 sq. miles contributing
• 16 of surface area of Texas
• 25 Hydrologic Unit Codes (HUCs)

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WRAP Parameters Method
Stream Channels
Corrected Channels
Burned DEM
Stream Network
Flow Area Accumulation
DEM
Filled DEM
CN and Avg. Rain
Area, CN, Rain Accumulation
Control Points
Flow Distribution Parameters
original datasets
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Correcting RF3 Channel Lines

• Replacing open water boundaries with channel
  centerlines
• Deleting braided channels
• Removing or connecting broken channels
• Erasing interior dangling nodes

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Replacing Open Water Body Boundaries
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Deleting Braided Channels
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Flow Area Accumulation Grid
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Stream Network
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Why Build a Stream Network?

• Control point locations may match exactly to
  channel grid cells in the flow accumulation grid.
• Snapping control points to the stream network
  lines ensures the control points will define the
  correct outlet locations on the flow accumulation
  grid.
• Downstream control points can be identified on
  the stream network and incremental subwatershed
  changes in hydrologic parameters can be computed.

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67 Control Points
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WRAP Parameters Method
Stream Channels
Corrected Channels
Burned DEM
Stream Network
Flow Area Accumulation
DEM
Filled DEM
CN and Avg. Rain
Area, CN, Rain Accumulation
Current Status
Control Points
Flow Distribution Parameters
original datasets