GREAT-ER Class Concept

Frank Koormann frank.koormann at
Mon Aug 23 11:13:26 CEST 2004

Dear all,

as you may have noticed a new CEFIC LRI Project has started to add a
first and rather simple sediment component to GREAT-ER: Simple
equilibrium concentration in sediment as described for the WATER model
(which is implemented by GREAT-ER). 

The parameters needed for this approach are already in the GREAT-ER
database, as fields in the stretch class table. Some of these have to be
made editable by the user. I will illustrate our plans from the 
parameter editing point of view, describe some consequences to the 
class concept and I would like to ask for your comments on this:

The class concept 
(implemented by GREAT-ER 2.0 as well as 1.0) allows to define 
distinct parameter sets for different types of stretches in a catchment.
However, in personal communication it always has been considered as
somewhat experimental and not of much use since the parameters have to
be defined during catchment preprocessing. They cannot be
changed/displayed later on.

For the sediment module at least the suspended solids concentration
(SS_RIVER) has to be editable by the user, we will add this to the 
environmental parameters. As a consequence a single SS_RIVER probability
density function will be applied for the entire catchment. We are
planning to add also the other parameters needed for the equilibrium
calculation to the environmental parameters:
        f_oc:    Organic carbon fraction of suspended solids in river
        rho_sed: Dry sediment density
        eps_sed: Volumetric water fraction of the sediment

As for all environmental parameters default values will be defined which
will overwrite the values from river classes. For users who really want to
work with classes will will add a choice to the model mode dialog:
- Use class parameters
- Use environmental parameters

Your thoughts?

Thanks in advance,

Frank Koormann                             <frank.koormann at>
 Professional Service around Free Software       (
 FreeGIS Project                                 (

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