Task B2: Updating Hydrologic-Connectivity Attributes

Overview: This procedure will identify and repair the broken links between the previously customized basins and the newly downloaded basins that were mosaicked in Task B1. Broken links will be repaired by updating the hydrologic-connectivity attributes in the basin_mosaic table.


You should have the basin_mosaic and derivedstr_all shapefiles in your view.

  1. Make basin_mosaic the active theme. From the Bsn-Tools menu, select Validate Basins. A text file named qctabl1.txt will be generated listing all of the basins with broken links. Open this text file so you can refer to it during the next steps.

  2. In the qctabl1.txt file, there will likely be lines with "Basin ZZZ has invalid parent YYY". We need to select each "Basin ZZZ" in the basin_mosaic shapefile. To do this, make basin_mosaic the active theme and open its attribute table. Click the Query button and build the following query:

    ( [Basin_id]= ZZZ) or ( [Basin_id]= ZZZ) or ... ( [Basin_id]= ZZZ)

    where ZZZ is each of the Basin_id values listed as having invalid parents in qctabl1.txt. Click New Set and close the Query window.

  3. For each selected basin, zoom in and make sure there is not a gap or overlapping basin that is causing the broken link. If you do not find any gaps or overlaps, proceed to the next step. If you do find a gap or overlap, the best solution is to repeat Task B1.

  4. For each "Basin ZZZ", we will set the "invalid parents" to 0. From the Table menu, select Start Editing. Select the Parent_id field by clicking its header. Click the Calculate button. In the Field Calculator window that appears, enter 0 in the box under [Parent_id]=. Click OK. The invalid Parent_id values should be changed to 0.

  5. We now need to link each "Basin ZZZ" with the immediate downstream basin. With the table still in edit mode, zoom in to each "Basin ZZZ" (these should still be selected) and, using the shift-key, select the next downstream basin. From the Bsn-Tools menu, select Link Selected Basins. This will update the Parent_id field for each "Basin ZZZ". Note: The Link Selected Basins tool can be used on each "Basin ZZZ" and downstream basin pair separately or on all pairs as a group.

  6. Now that we have repaired the invalid Parent_ids, we need to update the Upstream* fields. Make sure basin_mosaic is still the active theme. From the Bsn-Tools menu, select Add Upstream Links.

  7. To make sure all links have been repaired and the hydrologic-connectivity has been restored, run Validate Basins from the Bsn-Tools menu. If there are no errors, you are now ready to prepare the shapefiles for localization.

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