REBEKA2 News

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2020-11-09: Information on calculating the proportion of discharged NH4-N !!

Warning! The discharge portion f is only calculated in almost the same way as specified in the RW guideline without an inflow file:

  • without an inflow file:
    f = discharged NH4 load / (discharged NH4 load + NH4 load from catchment)
    according to guideline: f = discharged NH4 load / NH4 load from catchment
    => the difference will be fixed in the next update

  • with an inflow file:
    f = discharged NH4 load / (discharged NH4 load + NH4 load from all catchments above)
    according to guideline: f = (discharged NH4 load + discharged NH4 loads of all overflows upstream of the same receiving water) / NH4 load from all catchments above
    => an exact calculation is not possible due to a lack of information from the above projects. For this reason, no value will be displayed in the next update when using an inflow file.

2018-08-28: New REBEKA Version 2.3.2.0 !!

Update to this version is chargeable (400 CHF for update from version 2.2), it offers the following improvements:

  • New option for fully continuous simulation (recommended for slow emptying of tanks or simulation/sizing of SABA's)
  • Calculation of NH4 discharge load of wastewater to check the minimum requirements according to the new stormwater directive (the quantity is also shown for already calculated projects - without recalculation)
  • Numerical display of the probabilities fullfilling the STORM limits and easy copying to the clipboard
  • Easy copying of all results (deterministic and stochastic) to the clipboard
  • Update of Help and User Manual (german, english, french)
  • Various other improvements and bug fixes
A detailed description of the improvements can be found here as a pdf file.

2018-03-20: How to calculate return periods of maximal overflow discharges?

Maximum discharge rates per rainfall event are not documented directly. In order to receive them, a trick has to be applied:

  • Set the area of the natural catchment to 0 so that only constant base flow is generated in the receiving water. Save the project under a new name and perform a deterministic simulation.
  • Now open the file [project name]_det.csv in Excel.
  • The difference of the two columns vf_q_max - nez_q_max are the maximum discharge rates in m3/s
  • Calculate this in a new column and sort the table in descending order by this column.
  • Enter the rank in a next column (highest value 1, next 2, 3 etc.)
  • Calculate the return period T in another column: $$T = \frac{L + 0.2}{k - 0.4} \cdot \frac {M} {L}$$where k = Rank, M = Number of years, L = Extent of the partial series (L = 2.7 · M, i.e. 27 values for 10 years).
  • For T = 1a the result is a rank of 10.5, i.e. the mean of the 10th and 11th highest value of the series. With the simple formula T = M/k you would get rank 10.
  • An example can be downloaded from here.

2017-11-07: Error in help and manual for the formula to calculate the reservoir constant of the natural catchment runoff

The correct formula to calculate the reservoir constant for the natural catchment runoff is as follows: $$k = 2 \cdot \frac{(\frac{A_{eff}}{100}\cdot L_{max})^{1/3}}{(J + 0.0001)^{1/2}}$$ (e.g. the constant in the denominator is 0.0001 and not 0.001 as written in the help and manual). The error hasn't in most cases a strong influence on the value of k.

2017-10-12: Hints for Simulation with Inflow File and No Direct Catchment Runoff

If simulation is only performed with runoff from file (e.g. area of CSS and SSS = 0 and EWG = 0) following points must be considered:

  • The inflow file must cover the time range of the simulation, i.e. inflow must start before first rainfall event and end after last rainfall runoff event. This is checked when the inflow file is selected.
  • The inflow file must correspond to the used rain, i.e. it must be taken into account that REBEKA2 does not carry out a completely continuous simulation. The computation is stopped after 5 x (maximum of the storage constants of CSS and SSS) after the rain event end. If the rainfall runoffs in the inflow are strongly delayed, any inflow which can lead to overflow discharge is not taken into account. By increasing the factor 5 (the variable fEventDuration in the INI file), a longer simulation can be forced.
    Caution: The file C:\Users\[username]\AppData\Roaming\Rebeka\Rebeka.INI must be changed, not the INI file in the program folder.
  • The sediment fraction must be set to 0, otherwise a percentage of the inflow is generated as additional sediment fraction.
  • In Rebeka.INI, the variable NoFirstFlush = 1 (Default: 0) should also be set to force the program taking the TSS concentrations of the inflow file. It is not sufficient to set the FF coefficients to 1. Because in this case an average concentration for each event is calculated from the accumulated inflow load and water volume over the event. With NoFirstFlush = 1, the resulting TSS concentration is calculated by mixing of inflow, DWF and rainfall runoff. If only inflow is present, the inflow concentrations are taken.
  • For other simulations the parameters in the INI file should be set to their default values: fEventDuration=5, NoFistFlush=0

2017-06-10: Simulation Hints

I would like to point out that REBEKA 2 does not perform a completely continuous simulation. The catchment runoff is calculated only for a specific duration after the rainfall end. This duration depends on the choosen reservoir constants of combined and separate sewer system. Default additional simulation time is (5 x maximum of both reservoir constants). Therefore it is possible that the emptying of a defined CSO or SSS tank is not completely modelled for small throttle flows and high storage volumes although an empty tank is assumed at the beginning of the next rainfall event. This can be checked from the results of a deterministic simulation as follows: There should be no TSS remaining in the tank after the simulation period if the efficiency is set to 0. If complete emptying occurs the TSS are carried to the WWTP (combined sewer system) or to the receiving water (separate sewer system). By increasing the factor 5 (variable fEventDuration in INI file) a longer simulation duration can be enforced.

2017-06-10: New location of INI file

Warning: For version 2.2.6.1 and above the relevant INI file is located in C:\Users\[Benutzername]\AppData\Roaming\Rebeka. The INI file in the program folder is only read during the first start of the program after installation and is copied to the mentioned folder.

2014-06-12: Following errors were found (Projekt1 and REBEKA DIM)

The limits of the parameter 'Degradation rate of organic matter' in Projekt1 are set incorrectly: 0.2 to 0.8 instead of 0.12 to 0.3. This has an impact on the cumulative probability of the O2 Depletion by TSS. If you have chosen this project as template for new projects then all these projects are affected. You can download a program here that browses through your projects (starting in the folder where the program were copied and all subfolders) and lists in two files affected and not-affected projects (csv-files). This can take a while if many subfolders exist!

REBEKA DIM: Due to a error lower, upper limit and distribution of the TSS concentration of rainwater is not shown in the table 'Parameter Variation'. Therefore mean value, lower and upper limit and distribution are fixed to 68 mg/l, 34 mg/l - 102 mg/l and lognormal.

Version 2.2 is available and has the following improvements

  • Runoff in the receiving water (Q, conc. of NH4-N and TSS) can now be read from file. This allows to use measurement data from BAFU gauges, modified measurement data (e.g. at a residual flow stretch) or generated data from other simulation software.
  • Graphical representation of rainfall events (by double-clicking a rainfall event in the rainfall table)
  • Detailed results for bedload events (begin and duration of movement before and after the overflow location)
  • Rainfall data files must not anymore be stored in the program folder
  • Path and filename of rainfall data are now stored in the project data file. This means that the corresponding rainfall data is now automatically loaded together with the project data.
  • All program settings are now saved in the project data file and are reloaded if the project data is loaded.
  • Hiding of individual impacts (hydraulics, NH3 or TSS) is removed.
  • Shortcuts to open the data editors of separate (Ctrl-T) and combined sewer system (Ctrl-M), receiving water (Ctrl-V) and natural catchment (Ctrl-N)
  • Several small improvements and bugfixes

Update to this version can be ordered here.

Issues in Version 2.1.9

  • An error with message "No inflow record for this time..." may occur during stochastic simulation if an inflow from file is used. Setting reservoir time constants to a constant value during stochastic simulation can solve the problem. Please contact me if the error persists. This error may also occur during merge of two flow files.
  • User with licence for version 2.1: Please install the patch with version 2.1.9.2 (you received an e-mail with the download link)
  • The calculation of oxygen depletion can be incorrect! There will be shortly a corrected version 2.1.9.2 available for download. Please inform us, if you encounter unrealistic values!
  • In the project example projekt1 the boundaries of the parameter "sediment fraction" of 0.35 to 0.7 are wrong. They should be 0.1 to 0.3!
  • If you run a stochastic simulation, the results of the first run with the values from the deterministic simulation can be wrong. This only influences the display of the results: the values of the det. simulation are possibly wrongly displayed in the charts. A corrected version 2.1.9.1 will be available for downloading. You will be informed by e-mail.

Issues in Version 2.1.3

Unfortunately we have detected further errors in the program:

  • If you choose a partial rainfall series (only specific months), TSS immissions are calculated incorrectly. At the moment there is no workaround for this error.
  • If an inflow from file is defined and the catchment area is set to zero, the overflow volume is wrongly calculated.
    Workaround: set the catchment area to a small value > 0
  • The current implementation of the linear reservoir shows a strong attenuation with small reservoir constants. We will change this and also allow reservoir constants smaller than the time step of 10 min.
We apologize these errors and regret that we have found them only now. We try to fix these errors in the next updates of the program.
If you have discovered other errors, please notify us.

Older News (in French)


Last Update: 09.11.2020