Build One-Click SWAT Model
What is it?
A 'One-Click' model is a SWAT model created using pre-selected options. In this process, user inputs are not needed during the model building process. Once the model building is completed, SWAT model is run and results are displayed. The displayed results are water balance maps, 3D model view and simulated stream flow with observed output from a USGS station if USGS station is selected.How to use it:
Watershed delineation options
Select DEM resolution and DEM cell threshold for stream creation. Multiple DEM resolutions are available at SwaNET data repository. Please select DEM resolution according to your model area. For a larger area, select 300m or 1000m resolution DEM. For a smaller area, select 90m or 30m DEM.Around 1 to 1.5% of the total number of pixels is sufficient as DEM cell threshold. DEM cell threshold is the number of DEM cells required to form a stream. If a cell has at least the number of threshold cells draining into it, the cell will be a part of stream. Selecting lower number of threshold cells results in higher number of subbasins and vice versa.
HRU creation options
Select land use map and soil map resolutions based on model area. For larger area, select 400m land use/soil maps. Pleas note, 30m land use and soil maps are only available in in US.Select slope bands. Single slope band us sufficient for relatively flat area. If the model area has large variation in elevations, two to three slope bands should be used.
HRU selection options
Select single HRU per subbasin: There are two options for choosing single HRU per subbasin: dominant landuse, soil, slope and dominant HRU. Dominant landuse, soil, slope chooses the landuse with the biggest area in the subbasin, the soil with the biggest area in the subbasin, and the slope range with the biggest area in the subbasin and uses them for the whole subbasin. Dominant HRU selects the largest of the potential HRUs in each subbasin and makes its landuse, soil and slope range the ones chosen for the whole subbasin.Select multiple HRU per subbasin: There are three options for creating multiple HRUs per subbasin: target number of HRUs, filter by area, and filter by landuse, soil, slope.
To filter HRUs by target number of HRUs, enter a number as a multiple of number of subbasins. If the number entered is 4 and the number of subbasins created is 20, target number of HRUs is 80. Select how to filter out the smaller HRUs: as a percentage of subbasin or absolute area.
To filter the smaller HRUs by area, enter a threshold number and select how to filter. Filter option can be either percentage of subbasin or absolute area. The HRUs that fall below the threshold will be removed.
To filter HRUs by landuse, soil, and slope, enter the threshold landuse, soil and slope values in the respective input boxes. The threshold values can be either percentage of subbasin or absolute area.
Write SWAT input file options
Select weather generator database: Multiple weather databases are available for the US. If the modeling area is outside the US, user must select 'WGEN_CFSR_World (Global) option.Add point sources: Dummy point sources are added to each subbasin if the option 'Add dummy point source files to subbasins'.
Heat unit calculation: Check 'Use weather database to calculate heat units to maturity (US only)' option if the modeling area is in the US and this method is desired. Selecting this option for the modeling area outside the US may result in erroneous heat units for crop to maturity.
Compare results with USGS monitoring data
This option allows users to add USGS sensor data stations as outlets. To use this option, users must have downloaded USGS sensor data.If no data has been downloaded, close all the interfaces to go to the main SWAT interface. Click Utilities-->USGS monitoring data-->Extract data. Draw a box in the model area and Click "Save Shape". Follow the menu to download data.
Once the data is downloaded, come back to this interface and click 'Load Stations'. If you have not selected model area, you may be asked to draw model area. Click 'Draw Shape' and draw an area around the SWAT model area. Once done, click 'Save Shape'. Click 'Load Stations'. USGS stations within the selected area are displayed as markers.
To view data availability, click any marker. A new pop-up window with site name, number of field observation data points, start date, end date and link to USGS sites appear.
To view the field measurement data, click 'View Field data'. Note: User must have checked 'Full Site Attributes' option while downloading USGS monitoring data, otherwise no data will be available to view.
To download and view daily data, click 'View daily data'. This option downloads daily data from USGS station in real time, and plots it.
To add the USGS station as an outlet, click 'Create outlet'. The station is added to the station list.
Once all the desired outlets have been added, select 'Snap threshold'. If any outlet is within the threshold value, the USGS stations are snapped to the nearest stream and subbasin outlets are created.
Outputs
Once the model building is completed following outputs will be displayed:1. Water balance map
2. 3D view
3. Comparison chart of SWAT output VS observed data. If no USGS station is selected or observed data is not available for any USGS stations, output from the default outlet is plotted.
If multiple USGS stations are selected, only one USGS observed data will be compared with the SWAT output.
1. If daily data is available for the first USGS station, the daily data from the station is plotted.
2. If daily data is not available, and the field measurement data is available, the field measurement data from the station is plotted.
3. If both daily and field measurement data are not available, the same process is repeated for the second station and so on.
4. If any observed data is available, the SWAT simulation period is adjusted to include that period and compared.