🌾 SwaNET · Quick Tutorial 15 of 19

Outlet Selection & Finalize Watershed

This tutorial explains how to select outlets, merge small subbasins and finalize watershed delineation.

SwaNET Tutorial 15Prereq: MAGNET4WATER Account9 min read📄 Derived from PDF source

1Outlet selection

Figure 1. Outlet selection tab on main menu
Figure 1. Outlet selection tab on main menu

Outlets are the points in the drainage network of a sub-watershed where streamflow exists the subwatershed area. Adding sub-watershed outlets at the monitoring locations is particularly useful in comparing measured and simulated flows and concentrations. Outlet selection also determines the extent of the watershed.

Default outlet

To use the default outlet option, check ‘Use default outlet’. This option selects the point in the stream network that has the largest drainage area.

Figure 2. Outlet selection
Figure 2. Outlet selection

a. Check ‘Use default outlet’ under ‘Select outlets’. b. Click ‘Create watershed’

Using USGS gauging stations

Setting USGS gauging locations as the subbasin outlet allows users to directly use the USGS sensor data during model calibration process. To use USGS stations as subbasin outlet, user must have downloaded USGS sensor data using the Magnet main platform. To download USGS sensor data follow these steps: a. Go to the Magnet platform and click ‘Analysis’ → ‘Data Explorer’ → ‘USGS Sensor Data’.

Figure 3. Default outlet selection
Figure 3. Default outlet selection

b. If sensor data has previously been downloaded, a prompt asks whether to load existing data or download new data. Click ‘Cancel’ to download new data.

Figure 4. USGS data download menu
Figure 4. USGS data download menu

c. Zoom to the point of interest and draw a rectangle around the area of interest. Click ‘Conceptual Model Tools’ on top of the Magnet platform main menu. The menu expands. Click ‘SaveShape’. The boundary is saved.

Figure 5. Prompt for loading previously downloaded data
Figure 5. Prompt for loading previously downloaded data

d. A data download interface appears as shown below. Under ‘USGS Sensor Data’, check ‘Full Site Attributes’ and ‘Remove sites with no data’ under ‘USGS Sensor Data’. Make sure that ‘Groundwater’ is unchecked, and ‘Surface Water’ is checked. Click ‘Extract Sensor Data’.

Figure 6. Selecting area of interest for downloading USGS data
Figure 6. Selecting area of interest for downloading USGS data

e. Sensor data are extracted, and locations are shown on the map. Click on any location to view its information. If no data is available within the selected area, a prompt appears showing that no location is found.

Figure 7. Options for downloading USGS surface water data
Figure 7. Options for downloading USGS surface water data

Once downloading is complete, go to the SwaNET platform for selecting outlets. Once the USGS sensor data is downloaded, follow these steps to add USGS stations as outlets. f. Check ‘Use USGS stations’ under ‘Select outlets’ and click ‘Load Stations’. A prompt appears to ask if the USGS sensor data has been downloaded. Click ‘OK’. If no domain is selected, a prompt appears warning that no domain/select polygon found. Click ‘OK’.

Figure 8. USGS stations loaded
Figure 8. USGS stations loaded

g. The interface is updated. Click ‘Draw Shape’ and draw a rectangle around the model area. Click ‘Save Shape’.

Figure 9. Loading USGS stations
Figure 9. Loading USGS stations

h. Click ‘Load Stations’ one more time. A prompt appears to ask if the USGS sensor data has been downloaded. Click ‘OK’. Another prompt appears indicating that the polygon found. Click ‘OK’. USGS stations are loaded and their locations are displayed on the background map.

Figure 10. Drawing model domain
Figure 10. Drawing model domain

i. Click on any station location (denoted by pushpin). A new interface appears with the station information.

Figure 11. USGS stations loaded
Figure 11. USGS stations loaded

j. Click on ‘View Field Data’, to view the field measurement data. k. To view the daily recorded data, click ‘View daily data’. A new interface appears that allows users to select the time period to download the daily data. It also displays the time period for which daily data is available. Just click ‘OK’ or select the desired time period and click ‘OK’. Available daily data is displayed. l. To add subbasin outlet at the current station location, click ‘Create outlet’. Repeat the process until all the desired USGS stations are added as outlet. Please note that not all of the stations have daily data available. Close the properties interface. m. These stations can be further edited. To delete a station, select the station and click ‘Delete’. To delete all added stations, click ‘Clear’. To add all available stations, click ‘Add all’.

Figure 12. USGS station information
Figure 12. USGS station information

n. Next, select the snap threshold. Snapping is the process of placing the outlet in the stream network. If any outlet is outside the snap threshold, the outlet is ignored. If the newly added outlets are to append on existing outlets, check ‘Add to existing’. Click ‘Snap outlets’. The outlets are snapped to the streams and displayed using blue color.

Figure 13. Selecting USGS stations
Figure 13. Selecting USGS stations

Don’t forget to manually add an outlet to the main watershed main outlet following instructions below.

Draw outlets

a. To manually add outlets, check ‘Draw outlets’ under ‘Select outlets’. b. To add a new outlet, click ‘Add outlet’ and click on the stream where the outlet is to be added. Repeat the process until desired number of outlets have been added. To delete an outlet, select the outlet, and click ‘Delete outlet’.

Figure 14. Selecting threshold and snapping outlet
Figure 14. Selecting threshold and snapping outlet

c. Next, select the snap threshold. Snapping is the process of placing the outlet in the stream network. If any outlet is outside the snap threshold, the outlet is ignored. If the newly added outlets are to append on existing outlets, check ‘Add to existing’.

Figure 15. Manually adding outlets
Figure 15. Manually adding outlets

Click ‘Snap outlets’. The outlets are snapped to the streams and displayed using red color.

Figure 16. Snapping manually added outlets
Figure 16. Snapping manually added outlets

Upload outlet shapefile

Users can upload their own shape file for creating outlets. The shape file can either be a zip (.zip) file containing at least .shp, .prj, and .dbf files, or GeoJSON file . Upload a new outlet shape file: a. Make sure that ‘Upload outlet shapefile’ is checked’.

Figure 17. Outlets snapped to the stream network
Figure 17. Outlets snapped to the stream network

b. Check the box on the left of ‘Import’ and click ‘Import’. Browse to the file location, select the file, and click ‘Open’. The selected file is uploaded to the MAGNET server, and the file name is displayed. c. Click ‘Upload’. The shape is saved in the userSwaNET folder and plotted. Load previously uploaded outlet shape file: a. Make sure that ‘Upload outlet shapefile’ is checked’.

Figure 18. Uploading a new outlet shape file
Figure 18. Uploading a new outlet shape file

b. Click ‘Use Uploaded File’. A list of previously uploaded files are displayed. c. Click ‘Select File’ and select the correct outlet shape file. From the list. d. Click ‘Upload’. The shape file is imported to the SwaNET project and plotted. Please note that the user shape file cannot be combined with drawn outlets or USGS outlets. Once the outlets have been added, click ‘Create watershed’ to create subbasins.

2Merge subbasins (optional)

a. To merge small subbasins with their parent subbasins, click ‘Merge subbasins’ button. The button expands and displays merging options.

Figure 19. Loading a previously uploaded shape file
Figure 19. Loading a previously uploaded shape file

b. Double click on the subbasin numbers or select a subbasin number and click ‘Select subbasin’ under ‘Select subbasins to merge’. The subbasins added to the list on the right side. Multiple subbasins can be added to the merge list. c. To clear the list, click ‘Clear list’. To add again, repeat the process above until desired subbasins are listed. d. Click ‘Merge subbasins. The selected subbasins are merged to their parent subbasins. Repeat the process as needed.

3Finalize watershed

Once the outlets have been added, and merging is completed (optional), the watershed can be finalized. a. Check ‘Create River File’ to create river shape file (optional). This file used in other Magnet modeling platforms. b. Click ‘Finalize watershed’.

Figure 20. Merging subbasins
Figure 20. Merging subbasins

The watershed is finalized, and DEM/hillshade maps are cropped to the watershed extent.

Figure 21. Finalizing watershed
Figure 21. Finalizing watershed