Latest update June 10, 2012: first version of this page.
Delwaq is the generic Deltares finite volume water quality and ecology solver that has been linked to 1D network models (like Deltares' own SOBEK model) as well as both structured and unstructured 2D and 3D models (like Delft3D, Telemac, ROMS and Untrim). The program has been able to flexibly couple to all these hydrodynamic solvers without any major architecture redesign for over 20 year by strict separation of geometry, topology, quantities and process formulations. In fact, delwaq itself doesn't know anything about the model geometry; although this has been a major advantage, the lack of geometry data on the delwaq binary output files is starting to limit the wider uptake and hence we're looking at options to enable geometry data on the output file without limiting bothering the computational core with irrelevant data on geometric differences between the various hydrodynamic models. A common generic geometric description would be best such that delwaq only has to call a single routine to copy it to the output file. For this purpose we have selected the new CF unstructured grid proposal. What information do we need from the flow module?
- Number of segments A segment is a delwaq volume. Note that the volumes used by delwaq may be aggregations of the volumes used by the hydrodynamic solver.
- Volume aggregation A mapping of flow volumes to delwaq segments. The (internal) segments are numbered 1 to Number of segments. Note: in specific cases, delwaq may also run on a disaggregated grid, e.g. 3D reconstruction based on 2D results and the logarithmic velocity profile, or 1D subgrid reconstruction generalized to rotational-free flow reconstruction in 2D or 3D models. We'll not consider these cases here at this moment.
- Number of exchanges Number of connections amongst the segments as well as the number of exchanges with the outside world (boundary conditions).
- Segment/exchange topology For every exchange the from/to segments (as well as the "from-1" and "to+1" segments for higher order schemes). Virtual segments representing open boundaries are indicated using negative numbers, i.e. -1 to -Number of boundary segments.
- Volumes For every time step the volumes of all segments.
- Surface Areas The surface area of each volume (may be constant or may be time-varying).
- Flows For every time increment (i.e. time span between two times at which the volumes are given) the discharges for every exchange.
- Flow Areas For every exchange the cross-sectional area of the exchange.
- Depending on the application, for consistency one may also provide other quantities for each segment, e.g. velocity, bed roughness, shear stress, temperature, salinity, sediment concentrations, etc. as already computed by the flow module. Alternatively, such quantities may also be computed by the delwaq system itself.
The user needs to furthermore supply
- Substance Selection Selection of water quality and ecology quantities/substances that one wants to include in the simulation (a selection of the 500 predefined quantities or add your own).
- Process Selection Selection of the processes that should act on those substances (a selection of the 700 predefined processes or add your own).
- Parameter Selection Specification of the parameters associated with the selected processes; all parameters can be constant or time- and/or space-varying.
- Initial Conditions Obviously one will need initial conditions for all simulated water quality and ecology substances.
- Boundary Conditions Concentrations associated with the various open boundaries of the flow model as well as the mass of any emissions modeled as dry waste load in the delwaq model.
For the generation of the boundary conditions we'll need one additional bit of information from the flow model, namely the names of all open boundaries as well as their location and (negative) boundary segment numbers associated them.
Example of a netCDF file:
