## Guidelines for AGNPS-GRASS Output Interface (The Visualization Tool)

Current NPS models including AGNPS have very limited graphics capability for visualizing and analyzing the model output. A distributed parameter model should assist in pinpointing the critical areas where one needs to pay attention for controlling NPS pollution. Even though AGNPS gives detailed output, users often can not make use of it, due to lack of proper analyzation and visualization tools. Graphical displays of the results have proven to be a more effective and efficient way of interpreting the results and in making decisions than scaning through pages and pages of numerical output in the form of tables. The following sections discuss the visualization tool in detail.

r.agnps50.view

AGNPS Output Parameters

Various output options are available with the AGNPS model. Primary output given for watersheds being analyzed includes watershed area, cell size, storm precipitation, rainfall erosivity (EI), estimates of runoff volume, peak flow rate at the watershed outlet, area-weighted erosion, both upland and channel. Also given are estimates of the sediment delivery ratio, sediment enrichment ratio, mean sediment concentration, and total sediment yield for each of five sediment particle size classes. Also available is a nutrient analysis, which include N, P and COD mass per unit area for both soluble and sediment adsorbed nutrients, and N, P and COD concentrations in the runoff. Table 1 lists a summary of output parameters that can be obtained for each cell or all cells if desired.

Table 1: AGNPS output parameters at the watershed outlet or any cell

Hydrology output

- Runoff volume (inches)
- Peak runoff rate (cubic feet/second)
- Fraction of runoff generated within the cell

Sediment output

- Sediment yield (tons)
- Sediment concentration (ppm)
- Sediment particle size distribution
- Upland erosion (tons/acre)
- Amount of deposition (%)
- Sediment generated within the cell (tons)
- Enrichment ratios by particle size
- Delivery ratios by particle size

Chemical output!Nitrogen

- Sediment associated mass (pounds/acre)
- Concentration of soluble material (ppm)
- Mass of soluble material (pounds/acre)

Phosphorus

- Sediment associated mass (pounds/acre)
- Concentration of soluble material (ppm)
- Mass of soluble material (pounds/acre)

Chemical oxygen demand (COD)

- Concentration (ppm)
- Mass (pounds/acre)

Initially the visualization interface generates 17 maps (Table 2) from the ASCII output files of an AGNPS run. The generated maps can be saved for future evaluation of output. All maps are generated using the reclass principle of the GRASS GIS tool, thereby minimum disk space is required. The map from which all output maps were reclassed (cell number map, filename_cell_num, where filename refers to the AGNPS ASCII input/output file without its extension) should not be removed.

Table 2: List of AGNPS output maps created using Visualization tool

Cell number map

Hydrology output

- Runoff generated map
- Runoff from upstream map
- Runoff to downstream map

Sediment output

Erosion map
- Deposition map
- Sediment leaving the cell map

Chemical output

- Nitrogen associated with Sediment (generated) map
- Nitrogen associated with Sediment (leaving) map
- Nitrogen associated with Runoff (generated) map
- Nitrogen associated with Runoff (leaving) map
- Phosphorus associated with Sediment (generated) map
- Phosphorus associated with Sediment (leaving) map
- Phosphorus associated with Runoff (generated) map
- Phosphorus associated with Runoff (leaving) map
- COD associated with Runoff (generated) map
- COD associated with Runoff (leaving) map

Name of the AGNPS-GRASS Output Interface Program: r.agnps50.view.

Procedures to follow while executing the Output Interface (the Visualization Tool):

First start GRASS 5.x from a shelltool window with the mapset where the data resides.

Resize the graphics monitor to fit the full screen of the workstation and use the Dselect.mon program to select the monitor. The GRASS shelltool window should be at the right hand side bottom of the screen.

Execute the r.agnps50.view program from the shelltool window where GRASS is running

A Visualization Tool Input menu will appear on the shelltool window requesting the following data/information from the user:

Enter Watershed Map name: Enter the name of the watershed boundary map containing cell values greater than zero and zero's for cells outside the watershed boundary.

Enter the cell size in meters: The length of the side of a cell in meters for which the model was run is entered.

Enter Aspect Map name: Enter the name of the aspect map for the watershed. It should have been created for the same resolution as the cell size above.

Enter the ASCII AGNPS file name without its extension: Enter the ASCII AGNPS file name without its extension since the program takes the default extension of .dat and .nps for input and output of the model, respectively. These files should be in the current working directory, else give the full path with the file name.

Then hit the Esc key to continue. Always look for a message at the bottom of the ASCII screen for continuing the execution, if there is no message then hit Enter after answering the question else hit Esc to continue.

In the following sections, each output screen of the visualization tool is discussed. The visualization tool splits the screen into various screens to display the output of the model. The number of windows created depends on the type of output displayed. The tool always reserves an ASCII terminal (non graphics) for interacting with the user. The first screen (Figure 1) provides various options including a watershed summary (no graphics) and spatially distributed soil loss, nutrients, runoff and feedlot movement (graphics) output of a watershed.

Figure 1: Initial screen of the Visualization tool

    Visualization Tool Main Menu

    Output Display Options
    1. Watershed Summary including sediment (no graphics)
    2. Soil Loss (graphics)
    3. Nutrients Movement (graphics)
    4. Feedlot Analysis (graphics)
    5. Runoff Movement (graphics)
    6. Analyze Different Scenarios
    7. Save Output Maps
    8. Exit to GRASS (to come back type 'return')
    9. Quit
    Enter the choice (1-9):

Option 1 (Figure 1) displays the watershed summary for soil loss, runoff and nutrient movement at the watershed outlet. This output is displayed in the non-graphics window. The watershed summary can be accessed from any part of the visualization tool, providing an opportunity for decision makers/users to compare the detailed cell output with the watershed outlet output for making decisions.

Options 2-5 (Figure 1) move to the next screen (Figure 2) where the appropriate output option maps are displayed. This screen is divided into numerous windows depending on the output option chosen. The screen is divided in half, having a series of top row windows and bottom row windows with an ASCII terminal. The top row windows display the output maps (Table 2). A scale for each of the output maps is displayed showing the color and the numerical value associated with it. The color of the output maps range from green-yellow-red, with increasing intensity of output. The right hand top corner window displays the watershed map with cell numbers by laying a grid on top of it for reference. Below this cell number map, the aspect map of the watershed with arrows pointing in the flow directions is displayed. In the bottom row, two windows display the output and input statistics for any cell. The left window shows cell inputs. The output window shows a bar chart and key features of the output option statistics for the same cell. The default cell statistics displayed in the bottom row windows are the statistics for the outlet cell of the watershed. The tool provides error checking and also explains what to do at each step.

In the next section, options 6-9 of Figure 1 are discussed.

Analyze Different Scenarios: This option allows the user to visualize and analyze a different simulation for the same resolution of the original run. The user is asked to enter the name of the ASCII AGNPS file name without its extension. The AGNPS run that was started with the visualization tool is called the 'current' and the simulation that was selected using this option is referred as 'selected' hereafter in this documentation. The program checks the resolutions between the 'current' and the 'selected' runs and checks for the same file names. Then the program creates the 17 output maps (Table 2) and displays the 'current' and the 'selected' output maps on the screen in the top row windows. The default output is the sediment movement maps. Bottom row windows display the output histograms of the 'current' and the 'selected' simulations. The left bottom row window corresponds to the 'current' input/output window and the right bottom row window corresponds to the 'selected' input/output.

Under this option the user has the same options (Figure 2) discussed earlier in this document. In addition to this, the user can alter the output visualization/analyzation to other model outputs such as sediment, nutrients, feedlot or runoff movement. While using options 2 and 3 (Figure 2), the user is asked to select either input or output to view in the bottom row windows.

For options 5 and 8 (Figure 2), the user is asked to select either the 'current' or the 'selected' simulation results to view in a window.

This option is one of the strongest feature of the visualization tool for analyzing different scenarios simultaneously.

Save Output Maps: This option allows the user to save the maps created using the visualization tool. The user can save all or only those outputs of interest, which include sediment, N, P, COD, and runoff. The program asks the user to enter a map name for saving the output maps. The program attaches proper extensions depending on the type of outputs (Appendix 1). Please refer to the appendix 1 for the extensions of different map names. It also contains reserved map names that should not exist in the current mapset. Do not remove the filename_cell_num map, since all output maps created in the visualization tool are reclassed from the created cell number map.

Exit to GRASS (to come back type 'return'): This option allows the user to exit to the GRASS temporarily to perform normal operations under the GRASS GIS tool. To come back to the same menu in the visualization tool, type return and hit enter.

Quit: This option takes the user back the GRASS prompt and exits from the visualization tool. The output maps created will be removed from the current mapset, but will not affect those maps that are saved using the Save Output Maps option. If you plan to use output maps at some future time, be sure to save them.

Figure 2: Generic options screen of the visualization tool for spatially distributed output

    Cell input and output Display Options

    1. Zoom
    2. View a Cell
    3. View an area output
    4. Toggle between flow direction map/viewing area
    5. Show the watershed summary output
    6. Displayed range of output maps
    7. Display user's choice map
    8. Draw Cumulative and Frequency Distribution Stats
    9. Restore the initial screen
    10. Exit to GRASS (to come back type 'return')
    11. Quit
    Enter the choice (1-11):

Each of the options in Figure 2 is discussed below: Its usage and how this assists users or decision makers is described. These options can be used alone or in combination with other options.

1. Zoom: Allows users to zoom in or zoom out of any section of the watershed by choosing one of the displayed windows. Once the zoom operation is performed, the tool automatically adjusts or redisplays all the maps in the top row windows to the same area, enabling users to take a closer look at an area of interest. This option is particularly helpful on large watersheds. Once the Zoom option is selected, the tool requests for a window to perform zoom operations. The user has to use the left mouse key to click on one of the top row windows and then click on the right mouse key to complete the selection process. Then the zoom function asks the user to use the left mouse to click on a place to define the area in the selected window, and then drag the mouse to the desired location and click on the right mouse key to complete the zoom process. Always follow the instructions displayed on the ASCII terminal. Failing to do so can cause the program to stop. Similarly, the unzoom operation can be performed.

2. View a cell: This option allows the user to enter a cell number of interest to display the statistics of that cell's inputs and outputs in the bottom row of windows. The displayed bar chart depends on the type of option chosen in the initial screen (Figure 1). The cell number can be either entered directly using the keyboard in the ASCII terminal or the mouse can be used to point out a cell on the graphics monitor using the left mouse key after choosing one of the top row windows. The window selection process is detailed in the Zoom section. This feature is helpful to visualize characteristics of both inputs and outputs of a critical area.

3. View an area output: This option allows the user to select an area from one of the top row windows and displays the average input and output statistics for that area in the bottom row windows. Here also, the user is asked to select a window from the top row windows using the selection procedure explained earlier. Then using the left mouse key, the user selects a corner of the desired area and drags the mouse to build a box. Click the right mouse key to complete the process. This information is helpful to study the statistics of the critical areas and its neighbors. Using this option, one could estimate average inputs and outputs for a field which should assist in making further decisions.

4. Toggle between flow direction map and viewing window location: This feature is helpful when users use Zoom to view any particular section of the watershed. After a couple of zoom operations, users may loose track of which part of the watershed is displayed. This option toggles between the flow direction map and the whole watershed map showing a box around the current viewing area.

5. Show the watershed summary output: The summary at the outlet of the watershed for all the outputs is displayed in the ASCII (non graphics) terminal. This option is useful to correlate cell outputs with those of watershed outputs to make decisions.

6. Display ranges of output maps: This option allows users to visualize output maps (Table 2) for a specified range between maximum and minimum values of the output (Figure 1) chosen. This helps users locate critical areas easily. For example, users can use this option to display problematic areas that are exceeding the soil tolerance limit (T factor). Options are available to save the displayed maps for later reference, compare various scenarios or overlay one map on another in order to make decisions.

7. Display user's choice map: Users have an option to display a cell map, overlay a map on another map or display a vector map. The chosen map can be displayed on one of the existing windows or users have an option to create a new window anywhere in the graphics monitor to display the map. Further, the map chosen for display can be one of the AGNPS output maps (Table 2) generated from the AGNPS output files or one of the existing maps in the database. From of the users/decision makers point of view, this option is helpful to reach conclusions about management strategies. For example, by overlaying a field boundary or property boundary on an erosion map, fields within critical limits can be located. Combinations of various outputs can be viewed simultaneously on the designed graphic windows. On selection of this option, the user is prompted for the map to be displayed. If the user selects to display the map in one of the existing windows, then the selection of the window operation is performed followed by the selection of the type of display. This could be to display a cell map, overlay a map on another map or display a vector map. Maps are listed for selection. If the user selected the option to create a new window to display a map, then the program requests a location to start the window. Using the left mouse key, drag the mouse to create a box of desired size and click the right mouse key to end the process.

8. Draw Cumulative and Frequency Distribution Statistics: This option allows the user to view the percentage of cumulative and frequency distribution area curves for any of the output maps (Table 2) or selective input variables for either user specified ranges of intervals/classes or for 10 equal ranges of intervals/classes between the maximum and minimum of the selected variable. This option is helpful to see how that particular variable is distributed both cumulatively and the number of occurrences in that interval. It is believed this information in combination with spatial referenced maps could be of very useful in the decision making process. The steepness of the curve shows how that variable is increasing within a corresponding range. By choosing this option, the program requests a window to display the statistical curves. Then, the program asks the user to select either an input or output variable for which to draw the curves. The user then has the option of keeping the previously selected X-axis intervals/classes or can select a new range of intervals/classes. The selection of new ranges of intervals can be done in one of two ways. Either the user can select 10 equal intervals between the maximum and minimum of the selected variable or he can enter the ranges between the maximum and minimum values. In either case, the number of intervals can't exceed 10.

9. Restore the initial screen: This option restores the original or initial display screen that was initiated when one of the options from Figure 1 was chosen.

10. Exit to GRASS (to come back type 'return'): This option allows the user to exit to the GRASS temporarily to perform normal operations under the GRASS GIS tool. To come back to the same menu in the visualization tool, type return and hit enter.

11. Quit: This option takes the user back to the initial screen (Figure 1). If the user has created any maps using option 6, the program asks if these are to be saved before quiting.

Appendix 1: List of AGNPS output maps and reserved map names

    Hydrology output

    Runoff generated map					ro_gen		X.ro_gen
    Runoff from upstream map				ro_us		X.ro_us
    Runoff to downstream map				ro_ds		X.ro_ds

    Sediment output

    Erosion map						Sed_in 		X.Sed_in
    Deposition map						Sed_gen		X.Sed_gen
    Sediment leaving the cell map				Sed_out		X.Sed_out

    Chemical output

    Nitrogen associated with Sediment (generated) map	N_sed_in	X.N_sed_in
    Nitrogen associated with Sediment (leaving) map		N_sed_out	X.N_sed_out
    Nitrogen associated with Runoff (generated) map		N_ro_in		X.N_ro_in
    Nitrogen associated with Runoff (leaving) map		N_ro_out	X.N_ro_out
    Phosphorus associated with Sediment (generated) map	P_sed_in	X.P_sed_in
    Phosphorus associated with Sediment (leaving) map	P_sed_out	X.P_sed_out
    Phosphorus associated with Runoff (generated) map	P_ro_in		X.P_ro_in
    Phosphorus associated with Runoff (leaving) map		P_ro_out	X.P_ro_out
    COD associated with Runoff (generated) map		COD_ro_in	X.COD_ro_in
    COD associated with Runoff (leaving) map		COD_ro_out	X.COD_ro_out

filename: Refers to the AGNPS ASCII input/output file without its extension

X: Refers to the name supplied by the user. The maps are saved with the extension in the current mapset.

## SEE ALSO

r.agnps50.input
r.agnps50.run

AGNPS Page

Last changed: $Date: 2002/01/25 05:45:34 $