r.answers provides a menu of steps to complete the input required to run an ANSWERS simulation. Each simulation is treated as "project" by r.answers. The inputs collected for the steps completed are recorded under a project name, so that they may be copied or recalled for further completion or modification. The first menu one encounters when running r.answers includes functions to create a new project, work on existing projects, copy an existing project, and remove existing projects. The main menu (shown below) lists steps to be completed to prepare ANSWERS input, to run ANSWERS, plus other miscellaneous functions.
ANSWERS on GRASS Project Manager Main Menu Project Name: <sample> Status Option Description --------------------------------------------------------- 0 Quit 1 Set mask, region, and resolution 2 Catalogue soils parameters 3 Catalogue land use and surface parameters 4 Identify elevation-based input layers 5 Prepare rain gauge data 6 Identify outlet cell 7 Specify areas with subsurface drainage 8 Catalogue channel parameters 9 Define channel slopes 10 Specify BMP's in watershed 11 Prepare ANSWERS input and run simulation 12 Miscellaneous Command Menu Option: 0__Steps 1-11 record and display their status to the left of the step number. If a step has not been run, no status is displayed (as seen above). If the step has been successfully completed, the status will be listed as "done". In some cases, a change in one step will cause the need to run another step again, in which case the status will read "rerun". If a step has a status of "done" or "rerun", if it is run again it will attempt to offer previous inputs as defaults.
Interface Operation Notes Throughout r.answers two primary types of interface/input are used:
<RETURN> moves the cursor to next prompt field <CTRL-K> moves the cursor to previous prompt field <CTRL-H> moves the cursor backward non-destructively within the field <CTRL-L> moves the cursor forward non-destructively within the field <CTRL-A> writes a copy of the screen to a file named "visual_ask" in your home directory <CTRL-C> where indicated (on bottom line of screen) can be used to cancel operation
Steps 1 through 10 collect inputs (either maps from the currently available mapsets or other text/numerical inputs) in order to create or extract the necessary portions of ANSWERS inputs for that step. After steps 1 through 10 are done, step 11 can be run to assemble an ANSWERS input file. ANSWERS can then be run using the inputs, and the output from the simulation is captured and processed, as described under step 11.
+------------------------------------------------------------------------+ |Soil Parameters for ANSWERS (see ANSWERS Users Manual for more details) | +------------------------------------------------------------------------+ |1 total porosity (percent pore space volume of soil) | |2 field capacity (percent saturation) | |3 steady state infiltration rate (mm/hour) | |4 difference between steady state and maximum infiltration | | rate (mm/hour) | |5 exponent in infiltration equation | |6 infiltration control zone depth (mm) | |7 antecedent soil moisture (percent saturation) | |8 USLE 'K' | +------------------------------------------------------------------------+
After the soil parameters are input, a screen will prompt for groundwater release fraction and tile drainage coefficient, which will apply to the entire watershed. The tile drainage coefficient indicates the design coefficient (mm/day) of tile drains in those areas designated as having tile drainage. The groundwater release fraction is measure of the contribution of lateral groundwater movement or interflow to total runoff.
After this step is completed, it will provide an option to save the entered parameters to a file or printer for reference. ANSWERS soils inputs will then be extracted and stored. This step may be rerun to change any of the information. Previously entered information will be recalled and may be modified.
+-------------------------------------------------------------------------+ |Land Cover Parameters for ANSWERS (see ANSWERS Users Manual for details) | +-------------------------------------------------------------------------+ |1 short (8 characters) description of land use and management | | (program will attempt to use map category description, if any) | |2 mm of potential rainfall interception by land cover | |3 percentage of surface covered by specified land use | |4 oughness coefficient of the surface (a shape factor) | |5 m of maximum roughness height of the surface profile | |6 Manning's n (a measure of flow retardance of the surface) | |7 relative erosiveness (function of time and USLE 'C' and 'P') | +-------------------------------------------------------------------------+
After this step is completed, it will provide an option to save the entered parameters to a file or printer for reference. ANSWERS cover inputs will then be extracted and stored. This step may be rerun to change any of the information. Previously entered information will be recalled and may be modified.
To facilitate the modeling of a number of storms this step will prompt for a rainfall event name. The data tables entered will be stored in the ANSWERS database under the event name.
Rain gauge data for ANSWERS consists two columns of numbers. The first is Time (in minutes) and the second is Rainfall Intensity (in mm/hour). Decimal values will be rounded to the closest whole number. To input rain gauge data to the Project Manager, a file must first be prepared with rain gauge data. If multiple gauges are to be used, one input file is still used, data for each gauge are separated by '-1' flag in the "Time" (first) column. Data for multiple gauges should occur sequentially by gauge; so that data for gauge 1 is first in the file, data for gauge two is the second group of data, and so on.
Example rain gauge data input files:
+----------+------------------------------------------+ |one gauge | two gauges | +----------+------------------------------------------+ | 0 0 | 0 0 | | 10 3 | 11 1 data for gauge 1 | | 20 10 | 25 7 | | 35 22 | -1 <----- delimiter | | 55 9 | 0 0 | | 67 4 | 15 6 data for gauge 2 | |100 0 | 10 4 | +----------+------------------------------------------+
This step will prompt to determine if multiple rain gauges are to be used. If so, it will prompt for the name of a map that represents areas to be assigned to the given gauges. The number of categories and their value should match the number of rain gauges. Next the program prompts for the name of the rain gauge data file. The program reads the file and displays what it found to the screen for approval. Having this, it will create the appropriate ANSWERS input files.
To prepare channel data for use with ANSWERS, the following is needed: a raster map layer of the channels in the watershed and a description of width (meters) and roughness (Manning's "n") for each channel category found in the layer.
It is suggested that the aspect map from Step 4 be created in conjunction with the channel map, since ANSWERS will abort operation if a one channel element does not flow directly into another adjacent channel element.
If desired, a raster map may be used to define channel slope values. To do so, a raster map should be prepared with category values for channel slopes in tenths of a percent (i.e. a category value of 31 would indicate a channel slope of 3.1 percent).
Note: Even though channel slopes are an optional input to ANSWERS, this step must be run if only to say no map will be used.
1. ANSWERS Tile Outlet Terrace Assumptions:
- Trap efficiency of 90%
- Only lowermost terraces are described
Also, if a terrace exists only in a portion of an element, the assumption is made that all incoming flow is influenced by the BMP. Thus, elements which have only a small portion of the practice within their boundaries should not be given credit for the practice.
2. ANSWERS Sedimentation Pond Assumptions:
- Trap efficeincy of 95%
- Only ponds in upland areas should be defined. In stream
structures are treated differently.
Also, if a pond exists only in a portion of an element, the assumption is made that all incoming flow is influenced by the BMP. Thus, elements which have only a small portion of the practice within their boundaries should not be given credit for the practice.
3. ANSWERS Grassed Waterway Assumptions:
- The vegetated area with in the affected element is no longer
subject to any sediment detachment.
- The model deliberately prohibits deposition within
the vegetation of a grass waterway, since any waterway
that effectively traps sediment would soon fill and
become ineffective.
For each category found in the layer, you will be prompted for width of the waterway
4. ANSWERS Field Border Assumptions
- The vegetated area with in the affected element is no longer subject to any sediment detachment.
For each category found in the layer, you will be prompted for width of the field border.
Also, sediment deposition in channel elements. This step will prompt for names to use for new watershed maps it will create by extracting these data from the output. If the simulation event did not create sediment loss or deposition, or channel deposition for the scenario, the given map will not be created. To find out how to access the output files, see the description of step 12, below.
The project database is where r.answers stores all the inputs, output, and other non-map data associated with the project. See the "FILES" section (below) for more information. There are two sections to the project data, since rainfall data are kept in a separate directory. When using this step to access database files, the program will list both the project data and the rain data files, and ask which section you wish to access. Next you will be prompted for the name of the file to access. This request will be turned over to the "file handler program" which facilitates sending a file to the screen, copying to another file, or printing.
The project status function available under step 12 creates a helpful summary of the project, and then passes control to the "file handler program" for display, copying to a file, or printing.
Each project will create and use the following files in $LOCATION/answers/<project name>/data. For the most part, there isn't much to see, unless something is not working right. If that is the case, The first thing to check would be files listed here under the Output section or Input file. Furthermore, attempting to fix a problem by editing any of these files could prove to have unpredictable results. Once a problem is identified (with the input maps or parameters, most likely) fix the input maps if need be, run r.answers again to make any changes, such a using a different map or correcting parameters. Remember that if a map is changed the menu step that uses it must be run again to resample the inputs. Run step 11 again to create a new input file and re-run ANSWERS.
General project data
reclass reclass rules to create project MASK region project region coordinatesANSWERS Input file
answers_input file created to use as input to ANSWERS
ANSWERS Output
When ANSWERS is run, output from stdout is sent to answers_output and anything that may go to stderr is captured in answers_error. After that the output is cut into sections. (if something unpredictable happened when ANSWERS ran, then the output and the files extracted from it may be garbled; reading answers_output and answers_error may provide clues).
answers_output complete output from running answers answers_error errors captured when answers is run out_chnl channel deposition data out_sediment element sediment deposition/loss data out_text verbose input reiteration out_hydro outlet hydrograph dataThe outlet hydrograph data is broken into 5 files to use as input to d.linegraph
hydro_time time increments of simulation (minutes) hydro_rain rainfall (mm/h) hydro_runoff runoff at outlet (mm/h) hydro_sed1 cumulative sediment at outlet (kg) hydro_sed2 sediment concentration in runoff (mg/l)ANSWERS Element data
Element data files are extracted from input maps. Each line is data for a watershed cell element. When answers input is created, these files are used to create the element data section.
in_row_col watershed row and column number in_soil soil type in_cover land use in_elev slope and aspect in_chnl channel element data in_rain rain gauge number in_tile subsurface drainage flagANSWERS Predata
The following files are used to form the "predata" section of the answers input file.
chnl_predata description of channel types cover_predata description of cover parameters soil_predata description of soil parameters rain_predata rain gauge dataParameter data
These files are used by the project manager to "remember" parameters used to create the respective predata files, allowing the parameters to be read back by the program for editing.
chnl_data channel parameters cover_data cover parameters soil_data soil parameters
d.INTRO
d.rast.edit
d.rast.num
d.what.rast
r.slope
r.fill.dir
r.direct
parser