BAGIS-H Users Manual

1. Introduction

BAGIS-H is a tool set that was designed for the delineation of hydrological response units (HRU) in a watershed (i.e., AOI). An HRU is a landscape area that has relatively homogeneous hydrological response properties usually formed by the unique combination of terrain, soil, land cover, vegetation, and management practices. HRUs are the basic spatial units within which hydrological parameters are collected and summarized and used in hydrological modelling.

The quality of HRU delineation affects the hydrological model outcomes. Though the concept of HRU is simple, the procedures for delineating HRUs have not been well defined.

The uncertainty and quality of GIS data further compound the complexity associated with HRU delineation. Scientists use what they "think" are the best procedures and source data layers to delineate HRUs. As a result, the knowledge and practice of HRU delineation ...

GIS, with its powerful overlay functions, is a convenient tool for the delineation of HRU.

2. HRU Delineation Factors

Topography
Drainage
Land use and land cover
Vegetation
Geology
Soils

3. BAGIS-H

3.1 Overview

ArcGIS and ArcGIS addin
GUI
Weasel and BAGIS
General workflow
- 1. Select AOI (and explore the layers in the AOI) - list layer types
  2. Explore HRUs and specify output HRU
  3. Define HRU rules and template rules
  4. Refine HRU

3.2 System Requirements

Windows XP or Windows 7
ArcGIS 10 with Spatial Analyst extension

3.3 Installation, System Setup, and Data Preparation

BAGIS-H was developed as an ESRI addin. The addin file that has an esriaddin extension name can be installed on a computer that has ArcGIS 10 or higher. To install the addin, double-click the addin file and it installs itself. To remove an addin, use the Add-In Manager tool in ArcMap under the Customize menu.
If an upgrade is provided for BAGIS-H, it is recommended that you use the Add-In Manager to remove the old version before installing the new version. Restart the ArcMap program after uninstalling the old version and before attempting to install the updated version.
BAGIS-H uses only AOIs created by BAGIS as input. AOIs created in GIS Weasel are compatible with BAGIS-H as well. To add layers to an AOI created either by Weasel or BAGIS, please use the AOI Utilities tool on the Basin Analyst menu of BAGIS. Please refer to Section 6.1.4 (page 14) of BAGIS User's Manual for more information on this function. There is also an Import function available on the BAGIS-H AOI Layers viewer.
Experienced users may use ArcCatalog to replicate the structure and prepare the files. All AOIs must have a vector shapefile called aoi_v that defines the AOI boundaries. All layers must be in the same projection and clipped to the AOI boundaries. See the BAGIS Users Manual for more information.

3.4 Workspace File Structures

AOI folders:
- AOIs are created with BAGIS. BAGIS adopts the file organization structure used by NWCC and the USGS Weasel GIS tool. AOI folders have predefined structures generated and used by the BAGIS model (Fig 3.1). Users must not modify these model's file structures.

Figure 3.1. AOI folder structure.

HRU folder and subfolders:
- Internal HRU main folder (AOI_FOLDER/output/zones/)
  - Internal HRU subfolder (AOI_FOLDER/output/zones/HRUNAME/)
    - File geodatabase (HRUNAME.gdb)
      - HRU raster name: grid
      - HRU vector name: grid_v
      - Raster factor (rule) output name: RXXX (XXX: numbers from 001 to 999)
    - XML: log.xml

Figure 3.2. HRU folder structure.

4. Using BAGIS-H

4.0 Contiguous, Non-Contiguous HRUs, and HRU IDs

BAGIS-H allows users to create contiguous and non-contiguous HRUs. A contiguous HRU layer contains individual HRU zones each formed by areas that are contiguous and are enclosed within a single polygon. A non-contiguous HRU layer might contain an HRU zone that is not contiguous and whose areas are delineated by several non-contiguous polygons. The unique HRU zones are identified by HRU ID whose values are stored as the cell values in the raster format of the HRU layer or in the "ID" field of the attribute table of the vector HRU layer. For HRU layers that allow non-contiguous HRU zones, BAGIS-H stores the non-contiguous vector polygons of the same HRU zones as "multipart" polygons. Each multipart polygon has one matching attribute record in the attribute table, regardless how many polygons are used to define the multipart polygon. Users can locate the vector and raster HRU layers, called "grid_v" and "grid" respectively, in the File Geodatabase of the HRU. In addition to the "ID" field, the attribute table of a contiguous vector HRU layer ("grid_v") has "HRUID_CO" and "HRUID_NC" attribute fields; whereas the attribute table of a non-contiguous vector HRU layer has "HRUID_NC." All these ID fields mentioned above are used by BAGIS-H internally and should not be modified by the users. The ID values in these fields might be altered in subsequent HRU refinement processes. Users should not use these ID values as the key to relate the HRU zones to users' data.

In BAGIS-P, which is a separate BAGIS add-in for ArcMap (see BAGIS-P Users Manual for more information), a new ID field, called HRU_ID, is created during the HRU parameterization process and is stored in the vector representation of the HRU zones generated by BAGIS-P. The new vector HRU layer ("grid_zones_v") is a featureclass that can be found in the same File Geodatabase where the "grid" and "grid_v" layers are located. grid_zones_v is converted from the "grid" raster HRU zones layer based on the raster's cell value (i.e., the "VALUE" field). The HRU_ID column, then, is added to the attribute table of the vector featureclass and the values are assigned based on the cell value. The ID values in the HRU_ID field of the grid_zones_v featureclass match the ID values in the ~~"ID"~~ "GRIDCODE" field of the "grid_v" featureclass. Both the grid_v featureclass (created in BAGIS-H) and grid_zones_v featureclass (created in BAGIS-P) are used in BAGIS-P for different purposes:

- During model execution: the BAGIS-P parameter output tables are related to the HRU zones using the ID field in the attribute table of "grid_v" featureclass
- When viewing the parameter output using BAGIS-P's Parameter Viewer tool, the grid_zones_v file is used for displaying AOI parameters. The HRU_ID field is used for joining the parameter records stored in the parameter table to the grid_zones_v's attribute table. Please do not delete the HRU_ID field from the attribute tables in the grid_zones_v featureclass of HRU layers.

For users of eRAMs hydrological modeling system, BAGIS-P creates a new ID field called ERAMS_ID when the parameters are calculated. This ID is included when the HRU geometry and parameters are exported as a zipped shapefile. The values of this field are generated according to the location of each HRU relative to the stream. The farther upstream an HRU is located, the lower its ERAMS_ID will be. For nested HRUs, one with a smaller maximum flow accumulation value will always be upstream of the ones that have a larger value. HRU zones with the same max flow accumulation values indicate that they are not nested and their orders are assigned randomly. eRAMS uses these values as the HRU IDs in visualization and modeling. The BAGIS-P Parameer Viewer also uses this ID to display the parameter values inside BAGIS-P.

4.1 The HRU Analyst Toolbar

The BAGIS-H program is distributed as an ESRI ArcMap addin - BAGIS-HDxxx.esriAddIn (where xxx is the version number). Once the addin is successfully installed, users can access BAGIS-H from the HRU Analyst Toolbar (by selecting "Customize.../Toolbars/HRU Analyst").

The toolbar contains a collection of buttons, menus, and a combo box (Fig 4.1). Below is a brief summary of the toolbar controls from left to right:

AOI Layers Viewer button: This viewer is used to select a working AOI and to explore the layers associated with that AOI (section 4.1).
Define Zones button: This dockable window may be used to select a working AOI. It includes functions for exploring HRUs (sections 4.2 and 4.3), and defining HRU rules and template rules (sections 4.4 and 4.5).
Selected AOI: This read-only combo box displays the working AOI, if it is selected.
Refine HRU menu: This menu points to several tools used for modifying and refining HRU datasets created by the define tools (section 4.6).
Options menu: Contains miscellaneous tools for managing HRU data (section 4.7).

Figure 4.1. BAGIS-H main ArcGIS toolbar.

4.1 AOI Layers Viewer

Users should use BAGIS to create AOI folders before trying to use data layers in BAGIS-H. AOIs created in GIS Weasel are also compatible with BAGIS-H. To add additional layers to an AOI created either by Weasel or BAGIS, please use the "Import" button on the AOI layers viewer. Once you have organized the data into an AOI, use the "Select AOI" button on one of the dialog windows of BAGIS-H to select a working AOI.

There are three main categories of data in an AOI: DEM layers, PRISM layers, and user-provided raster and vector layers. Fig 4.2 illustrates the raster and vector layers that might exist in an AOI. BAGIS-H uses only the raster version of the data as input for analysis. Users can use the Vector to Raster tool from the Options menu to convert vector layers into raster layers. To view the layers in an AOI, just click (select) the layer(s) from the lists and click the "View Layers" button to add the selected layers to ArcMap.

Figure 4.2. BAGIS-HD AOI Layers Viewer.

4.2 Define zones: Explore HRU layers

Use the "Select AOI" button to select a working AOI. Near the top of the Define zones dockable window is a list of existing HRU datasets in the working AOI (Fig 4.3). Users can use the "View HRU" button to view the datasets in ArcMap, use the "View HRU Log" to examine the process history and parents of an HRU dataset (section 4.3), or use the "Delete HRU" button to remove the HRU dataset from the AOI.

Figure 4.3. BAGIS-H Define Zones dockable window.

4.3 Define zones: View HRU log

The Summary tab of the process log contains general information about the HRU dataset including where to find the HRU output layers on your file system, HRU statistics (polygon count, average size, and maximum size), and the date the HRU was created (Fig. 4.4). If the HRU was generated from a parent HRU, that information is included on this tab. The process logs for ancestors can be viewed using the "View HRU Log" button which will be enabled if a parent HRU exists.

Figure 4.4. BAGIS-H View HRU log display (summary tab).

There is a separate tab for each rule or process that was used to create the HRU dataset. Use the top "View Layer" button to add the output of a selected rule or process to ArcMap. The bottom "View Layer" button can be used to view the input layer for the rule. The rule tab displays general information about the rule including where to find the input/output layers on your file system and the original parameters that were supplied to the rule.

Figure 4.5. BAGIS-HD View HRU log display (rule tab).

4.4 Define zones: Parent template HRU

BAGIS-H provides the capability to derive an HRU from an existing HRU dataset. The list of available HRU parent templates populates from the HRU datasets in the working AOI (Fig. 4.3). Select a parent HRU and then choose the zones to be included in the new HRU. By default, all zones are selected. If a parent template and zones are selected, the rules will apply only to the area included in those zones.

4.5 Define zones: Setting the HRU name, defining HRU rules and rule templates

Before a rule can be run or an HRU dataset created, users must specify an output name for the HRU dataset in the text field near the middle of the dialog window.

To add a rule to an HRU definition, make a selection from the "Rule Type" dropdown list and click the "Define Rule" button. Below is a list of the available rule types and a brief definition of each. See Section 4.5.1 for the details of rule types.

Contributing Area: Divides an AOI according to flow direction. Choose from one, two, or three contributing areas
DAFlow-Type Zones: Supports the USGS model for simulating streamflow
PRISM Precipitation: Zone definition is based on PRISM precipitation layers. Allows annual, quarterly, or custom PRISM layer calculations
Raster Reclass (Continuous data): Reclass continuous data by supplying a range for each class and a reclass value
Raster Reclass (Discrete data): Reclass discrete data by providing reclass values
Raster Slice: Slice continuous or discrete data. Choose from equal area or equal interval slicing

Template rules are more complex than the rules defined above. They include multiple data manipulation processes and are intended to streamline processing. The input layer is pre-determined and default values are provided for all properties, although these may be overwritten.

Defining a template rule is similar to defining a rule. To add a template rule to an HRU definition, make a selection from the "Rule Type" dropdown list and click the "Define Rule" button. Below is a list of the available template rules and a brief definition of each. See Section 4.5.2 for the details of template rules.

Aspect: Reclassify and filter the Aspect layer from an AOI
Canopy: Filter, reclassify, and filter a vegetation density layer from an AOI
Land Use: Reclassify and filter a discrete land use layer from an AOI
Slope: Filter, reclassify, and filter the Slope layer from an AOI

After a rule or template rule is defined, it is added to the rule table near the bottom of the form. Defined rules can be modified or deleted by clicking on the appropriate button. Rules may also be run prior to generating an HRU by clicking the "Run Rule" button. When a rule runs successfully, its' status changes to "Complete". Completed rules can be viewed in ArcMap by using the "View" button in the "View column. Note that an output name for the HRU dataset must be entered before running a rule so that BAGIS-H knows where to store the output layer(s).

At least one rule or template rule must be defined before creating an HRU dataset. When the "Generate HRU" button is clicked all rules and template rules without a status of "Complete" are run. The output of these rules is "added" together to create an HRU dataset. Each unique combination of values creates a separate zone. Use the "Allow non-contiguous HRU" checkbox to indicate if the HRU zones are required to be spatially contiguous.

See Figure 4.6 below for an example of an HRU definition with one complete and two pending rules. There is no parent template HRU and the output HRU zones must be spatially contiguous. When HRU generation is complete the dockable window resets and the new HRU dataset name is added to the HRU Layers list. Use the "View HRU" button to see the output.

Figure 4.6. BAGIS-H Define Zones dockable window with rules and output HRU name defined.

4.6 The Refine HRU menu

The Refine HRU menu includes post-processing tools that act on HRU datasets created by the Define Zones tool. Below is a list of the available Refine HRU tools and a brief definition of each. See Section 4.6.1 for the details of the Refine HRU tools.

Eliminate: Selectively remove small HRU polygons (zones) by area or percent
Cookie-Cut: Extract portions of a parent HRU dataset using the selected zones of another HRU dataset
Stamp: Overlay the selected zones of an HRU dataset onto the parent HRU
Reclassify zones: Change HRU zone values based on a look-up-table created in this tool through interactive procedures
Assign Sequential HRU ID Numbers: Re-number HRU zones sequentially with no gaps for compatibility with the PRMS model
PRMS Radiation Plane: Add slope and aspect statistics to an HRU attribute table
Zonal Statistics: Calculate and add selected zonal statistics to an HRU attribute table

Figure 4.7. BAGIS-H Refine HRU menu.

4.7 The BAGIS-H Options menu

The options menu includes miscellaneous tools to extend the capabilities of BAGIS-H. Below is a list of the available Options tools and a brief definition of each. See Section 4.7.1 for the details of the Options tools.

- Vector to Raster: Converts a vector file to raster format and stores in user layers directory
- Generate HRU with an HRU Template: Review the rules/process for an HRU dataset. Generate a new HRU dataset using these rules/processes from another AOI
- Template rule editor: Customize an existing rule template or create a new one. Edit the input layer and/or rule parameters

View HRUs log: Displays the selected hru log as a formatted html page in your web browser
- Make Weasel HRU Zones: Saves an HRU dataset into a file format that can be used by the USGS Weasel tool
- About BAGIS-H: Credits and version information about the BAGIS-H tool

Figure 4.8. BAGIS-H Options menu.

5. Beyond BAGIS-H

5.1 Working with GIS Weasel

Unlike GIS Weasel, BAGIS-H stores the output HRU layers in an ESRI File Geodatabase, instead of as ArcInfo GRID. The HRU layers created in BAGIS-H cannot be used directly in GIS Weasel. Users must use the conversion tool on the BAGIS Tools toolbar to generate the GRIDs that can be used in Weasel. Please refer to the BAGIS Tools toolbar for instructions to make the conversion.

5.2 Creating HRU layers outside BAGIS-H

This is another issue related to the use of ESRI File Geodatabase (FGDB) in BAGIS-H. Users must follow BAGIS-H's database design specifications to create an HRU layer that is compatible with BAGIS-H. BAGIS-H stores the output HRU layers in FGDBs located in different HRU folders under the "zones" folder of an AOI. The FGDB has the same name as the HRU (folder) name. Say, if an HRU called My_HRU is associated with an AOI named My_AOI. Then you can navigate to the My_AOI\zones\My_HRU folder and find the MY_HRU FGDB (i.e., My_HRU.gdb). The FGDB may contain several layers created by BAGIS-H. The actual HRU layer is a raster layer called "grid." To create an HRU layer outside BAGIS-H, you need to follow the file structure. Users can use BAGIS-H's existing functions to import an HRU layer that is created outside BAGIS-H and convert the imported layer to a BAGIS-H HRU zone layer. Here is a summary of the steps to import an externally created HRU layer into BAGIS-H:

Make sure that the externally created HRU layer is a raster dataset containing only discrete integer values and is in the same projection as the AOI. If your HRU layer is a vector file (e.g., a shapefile), then see the following steps to convert the vector dataset to a raster dataset.
- In ArcMap's search window (Ctrl + F), search for "Feature to Raster" and open the tool.
- Set Input features to the input vector data, Field to an integer field that identifies unique HRUs, and Output Raster values to a raster dataset. Set Output cell size to the AOI's dem layer, i.e., [AOI folder] path]\surfaces.gdb\dem_filled.
- Click on the "Environments..." button to open the tool's environment settings dialog window. Expand the "Process Extent" and set "Snap Raster" to the AOI's dem layer as well. Click OK to dismiss the settings dialog window and run the tool to create a raster version of the input vector data.
Start ArcMap and open the BAGIS-H toolbar. Click on the "Set AOI" button to open the "AOI Layers Viewer" dialog window.
Click the "Select AOI" button to set the target AOI. The AOI path shows the path of the selected AOI.
Click on the "Import" button and select the externally created HRU layer. Once the layer is imported it appears in the Raster Grids panel in the AOI Layers Viewer dialog window. Users can use the "View Selected" button to view and verify the imported data.
Click the Close button to dismiss the AOI Layers Viewer dialog.
Please note that a discrete raster must have an attribute table to be valid in BAGIS-H. Users can right-click on a layer in ArcMap and see if the "Open Attribute Table" option is available. If the option is disabled (i.e., the raster does not have an attribute table), then one can open the Properties dialog window of the layer, select the Symbology tab, and set the raster rendering scheme to "Unique Values." ArcMap will ask if the user wants to create the attribute table of the layer. Click Yes to create the attribute table.
Click the "Define Zones" button on the BAGIS-H toolbar to open the main HRU generating window. Again, use the "Select AOI" button to set the target AOI if it is not set.
Enter the output HRU zone layer name in the "Output Layer Name" field. Make sure the layer name doesn't exist in the list of HRU layers in the AOI.
When using an externally created raster as the HRU zone layer, please check the "Allow non-contiguous HRUs" option next to the Output Layer Name field. This will maintain the one-to-one mapping of the reclassification. Please note that, even though the output HRU zones and the input zones have an one-to-one relationship, they might not have the same raster values. BAGIS-H does maintain a one-to-one look-up-table in the attribute table of the output HRU zone layer.
From the "Rule Type" pull-down list select "Raster Reclass (Discrete data)," then click on the "Define Rule" button to open the "Raster reclassification" dialog window. Change the Layer type to "Raster." The raster layer just imported appears in the layer list panel. Select the layer, verify that the Reclass field is set to "Value". Click the "Unique" button to propagate the values in the layer's attribute table to the recode table in the window and then click the "Auto" button to set the New Values field. Click Apply to dismiss the dialog window.
Click on the "Generate HRUs" button to complete the process.
In cases when the input zone IDs must be maintained, users can navigate to the zone layer's File Geodatabase in ArcMap Catalog, delete the "grid" raster, and rename the "r001" to "grid."

Appendices

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