The runoff information provided by Alpine3D as hourly runoff grids can be used as inputs for the PREVAH model in order to generate hydrological discharge (see D. Viviroli, M. Zappa, J. Gurtz, R. Weingartner, "An introduction to the hydrological modelling system PREVAH and its pre- and post-processing-tools", Environmental Modelling & Software, 24, 10, 2009, pp 1209-1222).

Workflow

In order to use PREVAH to compute the hydrological discharge, the following workflow must be carried out:

Running Alpine3D with runoff grids outputs;
Compiling the special version of PREVAH
Once Alpine3D has completed, run the included PREVAH using the runoff grids as inputs;
extract the discharge from the PREVAH output files.

This means that Alpine3D needs to be properly configured to generate the runoff grids (see runoff grids), the PREVAH wrapper needs to be configured to read the runoff grids and PREVAH itself needs to be configured for the catchment of interest.

Compiling the special PREVAH version

A special version of PREVAH is available within the Alpine3D sources as runoff/prevah_runoff/runoff_prevah.cc and must be compiled separately, relying on the included Makefile runoff/prevah_runoff/Makefile. In this Makefile, you might want to edit the variable MIODIR to point to the root of your MeteoIO installation. You also need to make sure you have both the g++ and gfortran compilers installed on the computer that will do the compilation. Then simply compile with "make".

Configuring the PREVAH wrapper

Since PREVAH is used more like a library tailored to the Alpine3D model, a wrapper is provided to call PREVAH. This wrapper is configured in the "runoff.ini" file. This file must contain the following keys:

in the [INPUT] section:
- COORDSYS, COORDPARAM
- TIME_ZONE
- DEM as well as the keys specific to the chosen plugin
- LANDUSE as well as the keys specific to the chosen plugin
- GRID2D as ARC as well as the keys specific to the ARC plugin: GRID2DPATH and if needed, A3D_VIEW
- CATCHMENT to provide the catchments definition (see Catchments definition sub-catchments definition)
in the [OUTPUT] section:
- COORDSYS, COORDPARAM
- TIME_ZONE
in the [ALPINE3D] section:
- RUNOFF_CFG giving the file and path to the PREVAH configuration file

The PREVAH wrapper is then started as "runoff_prevah" with two arguments: the ISO formatted start date and ISO formatted end date. For example:

runoff_prevah 2004-10-01T01:00 2005-10-01T00:00

PREVAH configuration

The PREVAH model must also be configured for the catchment of interest. This is within the file pointed to by the Alpine3D::RUNOFF_CFG key. This file is built with sections, sub-sections and values structure. The whole "control file" section must be filled (between [Begin control file] and [End control file]) while the extended options can be discarded.

[Begin control file]
[Identification]
Dischmabach                    ! Catchment name
46.8                           ! Latitude
43.3                           ! Official catchment area [km2] !
0.01                           ! cell surface in km**2
[End catchment identification]
[Paths]
../input/surface-grids/        ! Directory with inputs (grids and tables)
../output/tables/              ! Output directory for tables (meteo and runoff)
../output/grids/               ! Output directory for grids (meteo and runoff)
../output/runoff/              ! Directory for model state (runoff)
../output/runoff/              ! Directory with rot grids (runoff)
[End Paths]
[Grids]
dischma                        ! Basic Name
dhm                            ! DEM extension
dhm                            ! Interpolation limits extension
ezg                            ! Meteo zones extension
ezg                            ! Watershed limits extension for runoff module
lus                            ! Extension for land use map
[End Grids]
[Tuneable Parameters]
dischma                        ! General output name
  46.05                        ! Treshold coefficient for surface runoff , Default=30.0
  28.02                        ! Storage coefficient in hours for surface runoff, Default=10.0
 143.42                        ! Storage coefficient in hours for interflow, Default=75.0
  2963.00                      ! Storage coefficient in hours for baseflow, Default=2500.0
 723.46                        ! Storage coefficient in hours for quick basflow, Default=750.0
   80.56                       ! Maximal content of the quick baseflow storages, Default=150.0
0.1842                 ! Percolation rate in mm per hour, Default=0.1
[End Tuneable Parameters]
[Storage content]
1.0                            ! Anfangsspeicherinhalt Ob. Sp. RO+RH (mm)
-1.0                           ! Anfangsspeicherinhalt Unterer Sp.RG (mm)
-1500.                 ! RG (l/sec)
[End Storage content]
[End control file]

PREVAH outputs

The outputs are prefixed with the "general output name" given in section [Tuneable Parameters] and written in the "Output directory for tables" given in section [Paths]. The standard discharge is given in the {general output name}.std file in column "rges".