Transcript Calculating Hydrologic Parameters for Estimating Surface

Calculating Hydrologic
Parameters for Estimating
Surface Water Flow at Ungaged
Locations
Richard Hoffpauir
Water Resources Engineering
Flow (cfs)
Gaged Locations
Days
Ungaged Locations
Estimating Flow at Ungaged
Locations
• Proportional change in drainage area and
average upstream parameters
Qungaged
Qgaged
 Aungaged

 A
 gaged
 CN ungaged

 CN
gaged

 M ungaged

 M
gaged

 Otherungaged

 Other
gaged





Flow per Unit Area
Linear Relationship Assumed
Gaged
Ungaged
Drainage Area
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)
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
user’s withdrawl reliability.
Further complicating the scenario, the permitted volume
of withdrawl affects the flow and reliability for downstream users.
1997 Texas Senate Bill 1
• Comprehenisive regional water resources
planning for future demands and droughts
• Water Availability Modeling (WAM)
• Water Rights Analysis Package (WRAP)
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.
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
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.
Datasets Used for this Project
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•
•
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Grid: USGS 1-Degree DEM (1:250,000 accuracy)
Grid: U.S. Curve Number
Grid: U.S. Mean Annual Precipitation
Lines: EPA RF3 and NHD Channel Lines
(1:100,000 accuracy)
• Points: Control Point Locations
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
(HUC’s)
WRAP Parameters Method
Stream
Channels
Corrected
Channels
DEM
Burned
DEM
Filled DEM
Flow Area
Accumulation
CN and
Avg. Rain
Area, CN, Rain
Accumulation
Control
Points
original datasets
Flow
Distribution
Parameters
Stream
Network
Correcting RF3 Channel Lines
• Replacing open water boundaries with
channel centerlines
• Deleting braided channels
• Removing or connecting broken channels
• Erasing interior dangling nodes
Replacing Open Water Body Boundaries
Deleting Braided Channels
Flow Area Accumulation Grid
Stream Network
Length
17217.78
1670.071
23313.29
15163.22
53185.99
37846.51
14553.96
17510.71
45693.05
5149.188
12176.68
25176.16
9712.052
4391.909
15963.08
8274.701
20709.69
51993.05
6167.422
45903.93
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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.
67 Control Points
WRAP Parameters Method
Stream
Channels
Corrected
Channels
DEM
Burned
DEM
Filled DEM
Flow Area
Accumulation
CN and
Avg. Rain
Current Status
Area, CN, Rain
Accumulation
Control
Points
original datasets
Flow
Distribution
Parameters
Stream
Network