Table of Contents
Arc Hydro provides a structure for storing geospatial and temporal data to support hydrologic simulation models. These simulation models typically require geospatial inputs in addition to the core attributes provided by Arc Hydro. WRAP Hydro, for example, extends Arc Hydro in order to develop parameters required by the Water Rights Analysis Package (WRAP), a hydrologic simulation model developed by Ralph Wurbs at Texas A&M University. WRAP Hydro includes a data model based on Arc Hydro, and a toolkit that operates on the WRAP Hydro features to calculate WRAP parameters.
Another important development with WRAP Hydro is that it supports a schema for working with large raster datasets. The scheme divides the grids into manageable pieces that represent hydrologically consistent regions. Parameters may then be calculated from the resulting grids, with the results written as attributes on vector features. The vector features may then be merged, and the attributes consolidated to produce the correct parameters for the entire basin. The WRAP Hydro tools perform grid summarization and watershed delineation processes, along with attribute consolidation. The toolkit features batch and advanced processing tools.
The WRAP Hydro data model was developed by Hema Gopalan at
the Center for Research in Water Resources at the University of Texas at
Austin. Her thesis, provided at the bottom of this page, provides an excellent description of WRAP Hydro, including
an application of WRAP Hydro to the Guadalupe Basin in Texas. Following is
a summary of a portion of Hema's thesis describing how to implement WRAP Hydro.
How can I implement WRAP Hydro?
The following tutorial will lead you through the creation of a WRAP Hydro geodatabse. The tutorial covers the necessary base data, the pre processing steps, the calculation of model parameters, how regional data is stored, and how to edit the WRAP Hydro data.
Select the HUCs that make up the basin (4 in case of Guadalupe). Create a 10 Km buffer around the HUCs and call it BufferWatershed (in PreProcess). Select all the Hydro Edges that lie within this buffer and export it to PreProcess and call it WRAP Flowline.
Clip the DEM to the buffered area and process it using Terrain processing tool in Arc Hydro Toolset. Get the Agree, Fill and Fdr grids. For agree the DEM is burned with WRAP Flowline.
Select all dangling nodes on the boundary and export them to a separate file. Delete all the dangling edges from the network.
Build a network with WRAP Flowline as a complex edge. Assign HydroIDs to the edges. Delineate catchments for each stream segment of WRAP Flowline with source layer as WRAP Flowline and Field as HydroID using the Delineate Watershed tool in WRAP Hydro toolset. Call this WRAPCatchment. The DrainIds of the delineated catchments will be populated by the HydroIDs of the WRAP Flowline segment it is draining to.
Figure 3: Populating DrainIDs of Watershed
Build a relationship between WRAP Flowline and WRAPCatchment. Select all the streams that make up the basin export them to WRAPEdge in WRAP Hydro. Using the relationship, select those catchments that drain to the selected streams. Export these catchments to a separate file. Dissolve all the polygons to create a single polygon ‘basin’ which defines the boundary of the basin.
Create a mask of basin and clip the fdr grid to it
Figure 4: Clipping the Flow Direction grid
Copy the BaseControlPoint feature class to PreProcess feature dataset and call it SnapControlPoint. Change the location of the junctions so that they lie within 25 m from the WRAPFlowline. Delete the old network and build a new one with SnapControlPoint and WRAPFlowline and snap the junctions to the edges by giving a 25 m snapping tolerance. Make sure all the junctions are snapped. Assign flow directions. Do a find connected task by changing the tracing options to selection. Export all the selected SnapControlPoint features to WRAPJunction.
Export the BaseControlPoint file to WRAPHydro and call it ControlPoint.
Build a network with WRAPJunction and WRAPEdge, with WRAPEdge as a simple edge feature and a 25 m snapping tolerance. Assign flow directions to the network. Make a copy of the WRAPJunction feature class. Delete all the features from WRAPJunction and load the features back in from the ‘copy’ file using the Load objects command. This is done to split the edges on points where junctions are located. After loading the Junctions the flow directions have to be set again for the WRAPEdges
Use HydroID tables manager to set the initial HydroID values for Junctions and Edges. The HydroID is a nine digit integer. The Junctions start with a ‘1’ and edges with a ‘2’.
Parameters:
Next Downstream ID: the flow direction has to be set before running this tool. This parameter is populated in the NextDownID field in the WRAPJunction feature class. Find Next Downstream Junction in the ArcHydro toolset is used. For any junction that does not have a next down id, the field is populated as -1. this also serves as a check to see if all the NextDownIDs are correctly populated.
Figure 5: HydroIDs and NextDownIDs for WRAPJunction
Figure 6: Length Downstream Assignment
Figure 7: Hydro Id of WRAPJunction (RED) to Junction ID of WRAPEdge to DrainID of WRAPWatershed
Figure 8: DrainArea, AvgCN and AvgPR populated in WRAPWatershed
Figure 9: Illustration showing three WRAPJunctions whose values are accumulated downstream
Figure 10: Regional WRAPHydro schema format
1. Grids for each region (HUC) are processed separately with a 10 Km buffer. Basin boundary is created and preprocessing is done similar to previous method.
2. An outlet is placed at the most downstream location of each region. Care should be taken that no stream segment is repeated in any of the regions.
Figure 11: Placing outlets for sub regions
3. HydroIDs are assigned to each HUC prefixed with region numbers. A ‘1’ or a ‘2’ follows the region number depending on if it is Junction feature or Edge feature respectively.
Figure 12: HydroID assignment at regional level
4. WRAPWatersheds are delineated for each region and WRAPJunctions, WRAPEdges and WRAPWatersheds of all the regions are merged and exported to the WRAPHydro geodatabase. A network is built and connectivity between regions is checked. The Parameters are populated as done previously.
and ‘Batch Process HydroJunctions’
are used to incorporate new junction edits into the network. A watershed is
delineated for each new junction and the other parameters, NextDownID,
Drain_area, average curve number and precipitation values are populated
automatically in the respective fields. LengthDown field has to be populated
using the attribute tool in ArcHydro toolset. The new junctions are
automatically assigned HydroIDs in the same sequence as other junctions in the
layer.
Figure 13: Adding new Junctions
Figure 14: Removing a junction
Figure 15: Adding new stream edits
Hema Gopalan
Graduate Research Assistant
Center for Research in Water Resources
Department of Civil Engineering, University of Texas at Austin
(512) 471-0073
Note : Hema graduated in May and now works for the Florida Department of Environment Protection
Tim Whiteaker
Graduate Research Assistant
Center for Research in Water Resources
Department of Civil Engineering, University of Texas at Austin
(512) 471-0073
These materials may be used for study, research, and education, but please credit the authors and the Center for Research in Water Resources, The University of Texas at Austin. All commercial rights reserved. Copyright 2003 Center for Research in Water Resources.