B.11 Outputs

B.11.1 Mass Balance

TUFLOW FV supports mass balance outputs that assist with model understanding, calibration and assessment. These outputs are a suite of csv files that report timeseries of all time-accumulated volume and mass fluxes within a model domain, as related to all simulated quantities, other than temperature and pathogens. One csv file is generated for each simulated quantity’s volume or mass balance, and so is intentionally self contained. This allows users to complete their own mass balance analyses on a per simulated quantity basis, without additional post processing or reference to any other output files.

Each output csv file is named <fvc_name>_MASSBALANCE_<quantity_name>.csv, so for example the csv file for the salinity mass balance of simulation River_001.fvc would be named River_001_MASSBALANCE_SALINITY.csv, and written to the nominated results folder. Each csv file has several columns, each reporting a timeseries of mass or accumulated flux, and these columns vary between simulated quantities. The following columns are reported as the first five columns for all simulated quantities:

  1. Time
  2. Total instantaneous volume or mass of quantity, as computed from TUFLOW FV state variables (which is the same as the mass output):
  3. Accumulated fluxes across all QC and QC_POLY boundaries, summed to a single timeseries
  4. Accumulated fluxes across all Q boundaries, summed to a single timeseries. This does not include internal nodestring fluxes
  5. Accumulated fluxes across all WL, QN, WLS and WL_CURT boundaries, summed to a single timeseries. This does not include internal nodestring fluxes

Fluxes associated with ‘FC’ flux boundaries are excluded.

Following these columns, a series of bespoke accumulated fluxes are reported, and these depend on the quantity reported. After these bespoke accumulated fluxes, the following four columns are reported for all simulated quantities:

  • Summed accumulated fluxes for reported quantity, including boundary (columns 3 - 5 above) and all bespoke fluxes, with sign (direction) preserved
  • Instantaneous flux-based volume or mass at time \(t\), as computed from summing the volume or mass at time \(t-1\) and time \(t\) fluxes. This provides an alternative estimate of instantaneous volume or mass that is then compared with the volume or mass reported in column 2, and this comparison reported in the next column
  • Percentage error between the instantaneous volume or mass reported in column 2 and the corresponding flux-based estimate reported in the previous column
  • The number of times the quantity reported has been ‘turned over’ since the beginning of the simulation. This is computed by summing the accumulated absolute values of all fluxes and diving that sum by the original volume or mass. It is not intended to be an exact quantity to be used for flushing or similar analyses, but rather, to be interpreted as a quantity that provides an indication of the rapidity at which a quantity is cycled through a model domain. For example, a turnover value of 300 for VOLUME at the end of a one month simulation indicates that the modelled domain is dynamic and that water is cycled relatively quickly through the system. Conversely, a turnover value of 0.3 indicates the reverse - the simulated quantity is relatively stable and potentially stagnant. Additionally, if (for example) at the end of a simulation 250 WQ_DISSOLVED_OXYGEN_MG_L (dissolved oxygen) turnovers were reported, but only 10 VOLUME turnovers had occurred, then inferences can be made about the relative rapidity of dissolved oxygen processing compared to hydrodynamic flushing. This provides reportable insight into overall model behaviour.

Headers in output csv files are codes These codes are described for each of HD, AD, ST and WQ below, but have these common attributes:

  • V = Volumetric quantity
  • A = Areal quantity
  • MF = Mass flux
  • FV = TUFLOW FV output or computed from same
  • NS = Nodestring, encompassing WL, WLS, WL_CURT and QN boundary types
  • WQ = Water Quality output or computed from same
  • Q = Q boundary type
  • QC = QC or QC_POLY boundary types
  • TOTAL = Sum of all fluxes
  • PCT = Percent
  • TURNOVERS = As described above

B.11.1.1 HD

HD related mass balance output headers are presented in Table B.4.

Table B.4: HD Mass Balance Headers
Column Header Description Units
Volume <fvc_name>_MASSBALANCE_VOLUME.csv
TIME ISODATE Time
FV_VOL Instantaneous volume computed from TUFLOW FV state variables. Always a positive quantity. m\(^3\)
FV_MF_QC Accumulated volume fluxes across all QC and QC_POLY boundaries, summed to a single timeseries. Can be a positive or negative quantity. m\(^3\)
FV_MF_Q Accumulated volume fluxes across all Q boundaries, summed to a single timeseries. Can be a positive or negative quantity. m\(^3\)
FV_MF_NS Accumulated volume fluxes across all WL, WLS and QN boundaries, summed to a single timeseries. Can be a positive or negative quantity. m\(^3\)
FV_MF_EVAP Accumulated evaporative flux. Always a negative quantity. m\(^3\)
FV_MF_PREC Accumulated precipitation flux. Always a positive quantity. m\(^3\)
FV_MF_TOTAL Total of accumulated volume fluxes, with individual signs preserved. Can be a positive or negative quantity. m\(^3\)
MF_VOL Estimate of total volume computed from summing previous timestep volume and current timestep volume fluxes. Always a positive quantity. m\(^3\)
MF_PCT_ERROR The percentage error of the different between FV_VOL and MF_VOL. Can be a positive or negative quantity. %
MF_TURNOVERS Always a positive quantity. No units

B.11.1.2 AD

AD related mass balance output headers are presented in Table B.5. An ’_N’ in the file path refers to tracer number, which increments from 1 upwards to the total number of tracers simulated. One file per tracer is produced.

Table B.5: AD Mass Balance Headers
Column Header Description Units
Salinity <fvc_name>_MASSBALANCE_SALINITY.csv
TIME ISODATE Time
FV_SAL_MASS Instantaneous mass of salt computed from TUFLOW FV state variables. Always a positive quantity. tonnes
FV_MF_QC Accumulated salt fluxes across all QC and QC_POLY boundaries, summed to a single timeseries. Can be a positive or negative quantity. tonnes
FV_MF_Q Accumulated salt fluxes across all Q boundaries, summed to a single timeseries. Can be a positive or negative quantity. tonnes
FV_MF_NS Accumulated salt fluxes across all WL, WLS and QN boundaries, summed to a single timeseries. Can be a positive or negative quantity. tonnes
FV_MF_TOTAL Total of accumulated salt fluxes, with individual signs preserved. Can be a positive or negative quantity. tonnes
MF_SAL_MASS Estimate of total salt mass computed from summing previous timestep mass and current timestep mass fluxes. Always a positive quantity. tonnes
MF_PCT_ERROR The percentage error of the difference between FV_SAL_MASS and MF_SAL_MASS. Can be a positive or negative quantity. %
MF_TURNOVERS Always a positive quantity. No units
Temperature <fvc_name>_MASSBALANCE_TEMPERATURE.csv
Not used
Tracer <fvc_name>_MASSBALANCE_TRACER_N.csv
TIME ISODATE Time
FV_TRC_MASS Instantaneous tracer mass computed from TUFLOW FV state variables. Always a positive quantity. tonnes if TRC in mg/L
FV_MF_QC Accumulated tracer mass fluxes across all QC and QC_POLY boundaries, summed to a single timeseries. Can be a positive or negative quantity. tonnes if TRC in mg/L
FV_MF_Q Accumulated tracer mass fluxes across all Q boundaries, summed to a single timeseries. Can be a positive or negative quantity. tonnes if TRC in mg/L
FV_MF_NS Accumulated tracer mass fluxes across all WL, WLS and QN boundaries, summed to a single timeseries. Can be a positive or negative quantity. tonnes if TRC in mg/L
FV_MF_TOTAL Total of accumulated tracer mass fluxes, with individual signs preserved. Can be a positive or negative quantity. tonnes if TRC in mg/L
MF_TRC_MASS Estimate of total tracer mass computed from summing previous timestep tracer mass and current timestep tracer mass fluxes. Always a positive quantity. tonnes if TRC in mg/L
MF_PCT_ERROR The percentage error of the different between FV_TRC_MASS and MF_TRC_MASS. Can be a positive or negative quantity. %
MF_TURNOVERS Always a positive quantity. No units

B.11.1.3 ST

ST related mass balance output headers are presented in Table B.6. An ’_N’ in the file path refers to sediment fraction number, which increments from 1 upwards to the total number of sediment fractions simulated. One file per sediment fraction is produced.

Table B.6: Sediment Mass Balance Headers
Column Header Description Units
Sediment <fvc_name>_MASSBALANCE_SEDIMENT_N.csv
TIME ISODATE Time
FV_SED_MASS Instantaneous sediment fraction mass computed from TUFLOW FV state variables. Always a positive quantity. tonnes
FV_MF_QC Accumulated sediment fraction mass fluxes across all QC and QC_POLY boundaries, summed to a single timeseries. Can be a positive or negative quantity. tonnes
FV_MF_Q Accumulated sediment fraction mass fluxes across all Q boundaries, summed to a single timeseries. Can be a positive or negative quantity. tonnes
FV_MF_NS Accumulated sediment fraction mass fluxes across all WL, WLS and QN boundaries, summed to a single timeseries. Can be a positive or negative quantity. tonnes
FV_MF_NETSED Accumulated sediment fraction mass flux of net sedimentation (i.e. settling and erosion) acros the entire domain, summed to a single timeseries. Can be a positive or negative quantity. tonnes
FV_MF_TOTAL Total of accumulated sediment fraction mass fluxes, with individual signs preserved. Can be a positive or negative quantity. tonnes
MF_SED_MASS Estimate of total sediment fraction mass computed from summing previous timestep sediment fraction mass and current timestep sediment fraction mass fluxes. Always a positive quantity. tonnes
MF_PCT_ERROR The percentage error of the different between FV_SED_MASS and MF_SED_MASS. Can be a positive or negative quantity. %
MF_TURNOVERS Always a positive quantity. No units

B.11.1.4 WQ

WQ related mass balance output headers, and supporting explanatory text, are presented in Section 4.9.2 of the TUFLOW FV Water Quality User Manual, from Table 4.1 onwards.