Index: description.html
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RCS file: /home/grass/grassrepository/grass6/raster/simwe/r.sim.water/description.html,v
retrieving revision 1.3
diff -u -r1.3 description.html
--- description.html	13 Dec 2006 14:21:42 -0000	1.3
+++ description.html	29 Apr 2007 03:57:43 -0000
@@ -1,5 +1,5 @@
 <h2>DESCRIPTION</h2>
-<i>r.sim.water</i> is a landscape scale, simulation model 
+<i>r.sim.water</i> is a landscape scale simulation model 
 of  overland  flow   designed for spatially variable terrain, soil, cover 
 and  rainfall excess conditions. A 2D shallow water flow is described by 
 the  bivariate form of Saint Venant equations. The numerical solution is based
@@ -15,33 +15,45 @@
 the -d option in <a href="v.surf.rst.html">
 v.surf.rst</a> module. If elevation raster is already provided, partial derivatives
 can  be computed using <a href="r.slope.aspect.html">r.slope.aspect</a> module. 
-Partial derivatives determine the direction and magnitude of water flow. 
-Partial derivatives computed from terrain can be modified to include pre-defined  
-water flow (e.g. channels).<br><p>
-The module automatically converts data from feet to metric system using
+Partial derivatives are used to determine the direction and magnitude of water flow velocity. 
+To include a predefined direction of flow, map algebra can be used 
+to replace terrain-derived partial derivatives with pre-defined
+partial derivatives in selected grid cells such as man-made channels, ditches
+or culverts. Equations (2) and (3) from 
+<a href="http://skagit.meas.ncsu.edu/~helena/gmslab/reports/cerl99/rep99.html">
+this report</a> can be used to compute partial derivates 
+of the predefined flow using its direction given by aspect and slope.
+<br><p>
+The module automatically converts horizontal distances from feet to metric system using
 database/projection information. Rainfall excess is defined as rainfall intensity
-- infiltration rate.
+- infiltration rate and should be provided in [mm/hr].
 <!-- and can be  computed using   several available infiltration
 models (e.g.  Green-Ampt,  Holtan, etc.). (<font color="#ff0000">   find
 infiltration module in GRASS  - topmodel, casc2d</font> )-->
- Rainfall intensities
-are usually available from  meteorological  stations. Infiltration rate
-depends  on soil properties and  land cover. It  varies in space and time.
+ Rainfall intensities are usually available from  meteorological  stations. 
+Infiltration rate depends  on soil properties and  land cover. It  varies in space and time.
 For saturated  soil and steady-state  water flow it can be estimated  using
 saturated hydraulic  conductivity rates  based on field measurements or using
-reference values which can be found in literature.<br>
-</p>
+reference values which can be found in literature.
+Optionally, user can provide a runoff infiltration rate map <i>infil</i> in [mm/hr]
+that control the rate of infiltration for the already flowing water, effectivelly 
+reducing the flow depth and discharge.
+Overland flow can be further controled by permeable check dams or similar type of structures,
+the user can provide a map of these structures and their permeability ratio
+in the map <i>traps</i> that defines the probability of particles to pass
+through the structure (the values will be 0-1).
+<br> </p>
 <p>
-Output includes water depth raster map <i>depth</i>  in [m], 
-water   discharge raster map <i>disch</i> in [m3/s]. Error of the numerical
-solution can  be analyzed using <i>err</i> raster map  (the resulting water depth is an average, 
+Output includes a water depth raster map <i>depth</i>  in [m], 
+anda water discharge raster map <i>disch</i> in [m3/s]. Error of the numerical
+solution can  be analyzed using the <i>err</i> raster map  (the resulting water depth is an average, 
 and err is its RMSE).  Output site file <i>outwalk</i> can be used to analyze and visualize 
 spatial distribution of walkers at different simulation times (note that 
 the resulting water depth is based on the density of these walkers). Number 
-of theese output walkers is controled by <i>density</i> parameter, which says
+of the output walkers is controled by the <i>density</i> parameter, which says
 how many walkers used in simalution should be used in the output 
 <!--(<font color="#ff0000"> toto treba upresnit/zmenit, lebo nwalk ide prec</font>). -->
-Duration of simulation is controled by <i>niter</i> parameter.  The default value 
+Duration of simulation is controled by the <i>niter</i> parameter.  The default value 
 is 1000 iterations, to reach the steady-state may require, depending on the time step,
 complexity of terrain and land cover and size of the area, several thousand iterations. 
 Output files can be saved during simulation using <i>outiter</i> parameter 
@@ -52,10 +64,10 @@
 field or other landscape features influencing water flow. Simulation
 equations include a diffusion term (<i>diffc</i> parameter) which enables 
 to overcome elevation depressions or obstacles when water depth exceeds 
-a threshold water depth value (<i><i>hmax).</i></i> When it is reached,  
+a threshold water depth value (<i>hmax)</i>, given in [m]. When it is reached,  
 diffusion term increases as given by <i>halpha</i> and advection term 
 (direction of flow) is given as "prevailing" direction of flow computed
-as  average of flow directions from the previous hbetanumber of grid cells.
+as  average of flow directions from the previous <i>hbeta</i> number of grid cells.
 <br>
 <h2>
 NOTES</h2>