(GRASS Raster Program)
1) Basin map
2) Stream map
3) Drainage map
4) Accumulation map
5) Slope map
The other data requirements of r.water.fea are the parameters needed to calculate infiltration and the channel roughness parameter. Model parameters may be provided either in the form of maps or as values:
1) Manning roughness coefficient map or basin value
2) Saturated hydraulic conductivity map or basin value
3) Suction head at wetting front map or basin value
4) Effective porosity map or basin value
5) Degree of saturation basin value
On running r.water.fea for the first time, the directory "r.water.fea" is created under $LOCATION. When the user runs r.water.fea, the program will prompt the user for the project name. The project name refers to the directory that is created under the "r.water.fea" directory. All files (not maps) related to the analysis carried out by r.water.fea are stored under this directory. If the project does not exist then the user is further requested for the input maps. If the project already exists, then the program looks for the proper project related files to proceed with stopped work.
The user is asked for the following configuration modes: I) Rainfall mode: The rainfall mode is defined as follows:
1 = spatially uniform and constant in time
2 = spatially uniform but varying in time
If the user decides to use mode 2, then a mechanism is provided to allow creation of a rainfall rate file (described in step 4).
II) Basin-level hydrographs: This configuration mode allows the user to view intermediate hydrographs for every basin. The hydrographs will be displayed on the graphics monitor. Each basin is considered to be independent of every other basin in the analysis area.
III) Basin-level animation maps: This configuration mode allows the user to create time-series maps for later animation of flow depth for all the basins that have been analyzed. All animation maps use a multiplication factor of 1000. The map cell value divided by the multiplication factor yields the actual value of flow depth in meters. The user will require enough file space in the GRASS database for this configuration. All animation map names have the following naming scheme:
Here '#' represents the time step. One time step refers to 1/40th of the total monitoring time. Twenty maps are created at every other time step.
The basin and stream maps are displayed on the monitor when the user starts working on a project. The entire analysis is divided into a number of steps. The user is presented with a menu to proceed through the set of steps to facilitate easy changes to the simulation for a given analysis area or to stop analysis between menu steps and continue at a more convenient time.
The main menu is shown below:
Choose from the menu:
* 1. Process steps without breaks.
*-> 2. Select basins for simulation.
X 3. Extract topographical data.
X 4. Select hydraulic parameters and simulation time.
X 5. Basin simulation.
X 6. Simulate any particular basin.
X 7. Channel routing of basin hydrographs.
* 8. Stop.
You are starting from the beginning.
The "X", "*", and "*->" above have the following meaning.
Throughout the program the symbols described above change as the user moves from step to step. The message just above the Choice prompt signals the status of the program, and guides the user as to what should be the next step.
The user should avoid using these names to create other maps. Once these maps are created the user should not destroy them, if the user wishes to continue working on the project.
The program creates a file "timedata" in the project directory to store information from this part of the menu. If the user has selected the "Spatially uniform and time varying rainfall" mode (mode = 2), then the user is queried for the the name of a time file. If the file does not exist then a screen like the one shown below appears:
l l l.
[The time column must be filled in increasing order.]
1 ______ ______
2 ______ ______
3 ______ ______
4 ______ ______
5 ______ ______
6 ______ ______
7 ______ ______
8 ______ ______
9 ______ ______
10 ______ ______
11 ______ ______
12 ______ ______
13 ______ ______
14 ______ ______
15 ______ ______
c s s s
c s s s
l l l l.
AFTER COMPLETING ALL ANSWERS, HIT <ESC> TO CONTINUE
(OR <Ctrl-C> TO CANCEL)
It is important to note that the values in the time column should be in an increasing order. It is also not necessary to fill all the rows and the user can stop after filling only a few rows. The number of lines are limited to fifteen. If more than fifteen lines are required then the user will have to create the file using an editor. In that case the user should just type the time since commencement of rainfall (minutes) in the first column followed by the rainfall intensity (cm/hr) in the second column as shown below:
center; l l l c. 10 2.54 30 4.52 60 5.62
1.) Negative values of drainage direction inside basins maps cannot be accepted. Negative values are generated as a result of incomplete information regarding the basin drainage pattern (e.g., r.watershed produces negative values as a result of outflowing drainage basins).
2.) The drainage map should route the water and not form pits, lakes, or ponds. Note that this does not imply that the DEM by itself should not have any pits.
3) Interstorm modeling, interflow, or baseflow are not considered.
4) Backwater effects are not considered.
5) The kinematic wave analogy is appropriate where the land surface slope and channel slope are large. This may not be true in flat, marshy terrain and in slow, meandering river channels.
These are ASCII files that can be found in the "$LOCATION/r.water.fea/<project_name>" directory. The files have a format such that it can be imported to various analysis packages.
just when the program r.water.fea is run.
2. A small watershed can be analyzed by providing values of model parameters. However it is advisble to provide maps of various model parameters if there are many basins in the watershed. In the former case the value provided by the user shall be constant for the entire basin for which the value is queried. The user shall create the infiltration maps using the following set of rules. The map value divided by the multiplication factor yields the actual value in the described units:
center tab(:); ll lc. Parameter:Multiplication factor
Soil saturated hydraulic conductivity map (meters/sec):10,000,000
Manning roughness coefficient:1000
Soil suction at wetting front (m):1000
Soil porosity map (m3/m3):1000
3. If the user has provided a slope map that has zero slope value anywhere in the map, then a slope value of 5% is assumed for that cell.
4. It is preferred that none of the basins in the analysis area has more than 750 cells, as this will increase the computation time drastically. The number of cells in a basin can be controlled by setting the threshold value to small values when running r.watershed.
5. Using larger cells can speed up the analysis process significantly. It is important to note that r.watershed should be run for the resolution at which the user desires to run the r.water.fea analysis.