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

2. Gaged Locations

3. Ungaged Locations

4. Estimating Flow at Ungaged Locations
Proportional change in drainage area and average upstream parameters

5. Linear Relationship Assumed
Gaged
Ungaged

6. 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)

7. 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.

8. 1997 Texas Senate Bill 1
Comprehenisive regional water resources planning for future demands and droughts
Water Availability Modeling (WAM)
Water Rights Analysis Package (WRAP)

9. 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.

10. 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

11. 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.

12. Datasets Used for this Project
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

13. 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)

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

15. Correcting RF3 Channel Lines
Replacing open water boundaries with channel centerlines
Deleting braided channels
Removing or connecting broken channels
Erasing interior dangling nodes

17. Replacing Open Water Body Boundaries

18. Deleting Braided Channels

19. Flow Area Accumulation Grid

20. Stream Network

21. 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.

22. 67 Control Points

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