Main algorithm sources are rewritten from TMOD9502.FOR.
TMOD9502.FOR is available from http://www.es.lancs.ac.uk/hfdg/topmodel.html.

Thanks to Keith Beven.



[r.topmodel]
simulates TOPMODEL which is physically based hydrologic model.


Parameters:
(i)	elevation:	Rectangular elevation map

(i)	basin:		Basin map created by r.water.outlet

(o)	depressionless:	Depressionless elevation map

			This can be omitted if [elevation] map is already
			depressionless map.  If this is given, [depressionless]
			map will be used as [elevation] map.

(o)	direction:	This should be given with [depressionless] map.

(i/o)	belevation:	Study basin extracted elevation map

(i/o)	topidx:		Study basin extracted topographic index map

(i)	nidxclass:	Number of topographic index classes

(i/o)	idxstats:	Topographic index statistics file

(i)	parameters:	TOPMODEL parameters file

(i)	input:		Rainfall and potential evapotranspiration data file

(o)	output:		Output file

	Qobs:		Compare Qt with Qobs and calculate model efficiency

	timestep:	OPTIONAL output for given time step

	idxclass:	OPTIONAL output for given topographic index class


(i)   means input
(o)   means output
(i/o) means input or output


Flags:
	-i:		Without this flag, all input data, (i) or (i/o),
			should be given and intermediate output can not be
			input for run.
			
			In example, [belevation] map will be created from 
			[elevation] and [basin] every run.  However, every 
			[belevation] output map is the same and this is 
			useless process if [belevation] map is already given.

			With this flag, intermediate output can be input for
			run.  (i/o) parameters can be affected by this flag.

	-o:		Overwrite outputs

	-w:		No limit for 80 columns output