Source Data

This unit appears in the source section of a 1D Water Quality datafile. The unit simulates the impact of outfall, tributary streams and intake sites on river water quality. Alternatively the user can opt to store SOURCE data in separate files from the 1D Water Quality datafile

Description

Discharges from sewage treatment works, industrial complexes and tributaries can all carry dissolved and suspended substances into the river. Abstractions for the purposes of water supply or irrigation can remove a proportion of the dissolved and suspended substances from the river. Such features are simulated in the 1D Water Quality Solver using the SOURCE module. The module may also be used to set concentrations of a particular variable internally (i.e. notat a boundary node).

In order to determine the amount of a substance which is entering or leaving the model at a SOURCE node, two pieces of information are required. These are the discharge and the concentration of the substance in the discharge. At an outfall site (use OUTFALL), both these values need to be set in the SOURCE module. At an intake site (use INTAKE), only the discharge needs to be set because the concentration of the abstracted water will be that calculated within the model.

The discharge at an intake or outfall site may be specified statistically or as a time-history. Statistical discharges are based on the principle that they behave in some predictable way. For example a discharge from a sewage treatment works may show strong diurnal variations. Variations from day to day may be caused by industrial plants not operating at weekends. Seasonal variations of a similar predictable nature may also be evident. The daily, weekly and seasonal patterns of flow form shape functions. The product of the shape functions, annual flow and standard deviation of the flow for a particular time and date gives the statistical discharge (see equations below).

If the discharge has been set statistically, then the associated concentration must also have been calculated statistically.

At an outfall site the amount of material (discharge*concentration) entering the model is ADDED to the amount of material already in the model.

If the SOURCE module is being used to set the concentrations of variables internally, there is no need to specify a discharge at the SOURCE. Instead the concentration of the variable is IMPOSED at the SOURCE node.

The data associated with sources may be quite extensive, especially if an annual simulation is undertaken. The option exists in the 1D Water Quality Solver to store the SOURCE information separately from the 1D Water Quality datafile (see SOURCE, USER).

SOURCE data may be set for any of the transported variable names, listed at the end of each water quality process module, that are modelled by the 1D Water Quality simulation. The following variable names, with appropriate units, may be used at SOURCE nodes:

• Coliforms (user defined units)

• Decaying pollutant (user defined units)

• Conservative pollutant (user defined units)

• Salt (ppt)

• Temperature (C)

• Suspended sediment (mg/l)

• Dissolved oxygen (mg/l)

• Fast BOD (mg/l)

• Slow BOD (mg/l)

• Fast nitrogen (mg/l)

• Slow nitrogen (mg/l)

• Ammoniacal nitrogen (mg/l)

• Nitrite-n (mg/l)

• Nitrate-n (mg/l)

• Suspended particulate fast BOD (mg/l)

• Suspended particulate slow BOD (mg/l)

• Phytoplankton (mg/l)

• etrital carbon (mg/l)

• Orthophosphate (mg/l)

• Suspended benthic algae (mg/l)

• Detrital nitrogen (mg/l)

• Detrital phosphoros (mg/l)

• Adsorbed phosphoros (mg/l)

• Silicate (mg/l)

• Detrital silicon (mg/l)

In some cases it is possible to combine the different variable names together. The following combined variable names may be used:

The shape function for the daily variation can be derived from observed data as follows:

1. Assuming that a large data set of hourly flows (x (m/s)) measured for many days is available then the mean daily flow is calculated for each day, j.

                       (1)

2. The original hourly data for each hour is divided by the mean daily flow for the appropriate day to give a daily normalised function, y.

                      (2)

3. For each hour of the day, y is averaged over the number of days to give 24 values defining the daily shape function (z).

                       (3)

4. The values of y are then divided by the appropriate values of z, the shape function, to give a fourth set w. The standard deviation of w is then calculated for each hour of the day. Plotting out w in the form of a probability distribution will confirm whether or not the variation is Gaussian (ie normal).

                       (4)

   A similar process (steps I to III) can be applied to the weekly variation using mean daily flows as the raw data, and to the annual variation, based on the mean monthly flows. The standard deviation of w is only required for the hourly values.

5. The flow Q (m3/s) at any hour I on day of the week j during month k, will be given by:

                       (5)

Where:

The random fluctuation is introduced via the parameter n. This is calculated by randomly selecting a number between 0 and 1. This represents the probability associated with n standard deviations according to a normalised Gaussian probability distribution function.

Datafile Format

(1) STATISTICAL INTAKE/OUTFALL: When using the SOURCE module to specify data statistically, use:
Line 1                     SOURCE
Line 2                     STATISTICAL INTAKE or STATISTICAL OUTFALL
Line 3                     label (a)
Line 4                   variable name 'Discharge'
Line 5                     STATISTICAL
Line 6                   'OUTFALL' or 'INTAKE'
Line 7a-b               flwann(I) (I=1,12) (2 lines)
Line 8                     flwday(I) (I=1,7)
Lines 9a-c              flwhur(I) (I=1,24) (3 lines)
Lines 10a-c            varhur(I) (I=1,24) (3 lines)
Line 11                   annflw

If line 6 is the keyword 'INTAKE', no concentration data is needed so the following line is used:
Line 12                     END

Else if line 6 is the keyword 'OUTFALL', the following lines are used:

Line 12                     Variable name (a)
Line 13                     STATISTICAL
Line 14                     ADDED
Line 15                     'SEASONAL' or 'HOURLY'

If line 15 is the keyword 'SEASONAL' then the following lines are read:

Lines 16a-b                     pconst(I) (I=1 to 12) (2 lines)
Line 17                            END

Else if line 15 is the keyword 'HOURLY' then the following lines are read:

Lines 16a-c                     pconst(I) (I=1 to 24) (3 lines)
Line 17                           END

Where:

(2) TIME HISTORY INTAKE/OUTFALL: When using the SOURCE module to set the data as a time-history use:

Line 1     SOURCE
Line 2     TIME-HISTORY INTAKE’ or 'TIME-HISTORY OUTFALL'
Line 3     label (a)
Line 4     variable name 'Discharge'
Line 5     TIME-HISTORY'
Line 6    'DATE', 'SECONDS', 'MINUTES', 'HOURS', 'DAYS', 'WEEKS', 'LUNAR', 'MONTHS', 'YEARS', 'DECADES', or 'MULTIPLIER'

If the keyword 'MULTIPLIER' is used, then the following line is read:
Line 6a     fmult
Line 7    'INTAKE' or 'OUTFALL'
Line 8     ndat

If the keyword 'DATE' has been used the following line is read 'ndat' times:
Line 9a-end    ihour, imin, iday, imonth, iyear, flow

Else if the times are specified differently the following line is read 'ndat' times:
Line 9a-end    flow, time

If line 7 is the keyword 'INTAKE', no concentration data is needed so the following line is used:
Line 10    END

Else if line 7 is the keyword 'OUTFALL', the following lines are used:
Line 10    Variable name (a)
Line 11    HISTORY
Line 12    'DATE', 'SECONDS', 'MINUTES', 'HOURS', 'LUNAR', 'MONTHS', 'YEARS', 'DECADES', or 'MULTIPLIER

If the keyword 'MULTIPLIER' is used, the following line is read:
Line 12a    fmult
Line 13    ADDED
Line 14     ndat

If the keyword 'DATE' has been used the following line is read 'ndat' times:
Line 15a - end    ihour, imin, iday, imonth, iyear, conc
Line 16    END' or new variable name

Else if the times are specified differently the following line is read 'ndat' times:
Line 15a - end    conc, time
Line 16    END or new variable name

Where:

(3) INTERNAL BOUNDARY: When using the SOURCE module to set an internal boundary condition use:
Line 1    SOURCE
Line 2    TIME-HISTORY IMPOSED
Line 3    label (a)
Line 4    variable name 'Discharge'
Line 5    TIME-HISTORY'
Line 6    'DATE', 'SECONDS', 'MINUTES', 'HOURS', 'DAYS', 'WEEKS', 'LUNAR', 'MONTHS', 'YEARS', 'DECADES', or 'MULTIPLIER'

If the keyword 'MULTIPLIER' is used, then the following line is read:
Line 6a    fmult
Line 7    IMPOSED
Line 8    ndat

If the keyword 'DATE' has been used the following line is read 'ndat' times:
Line 9a-end    ihour, imin, iday, imonth, iyear, conc

Else if the times are specified differently the following line is read 'ndat' times:
Line 9a-end    conc, time
Line 10    END or new variable name (followed by new line 4 etc)

Where:

General

Only one SOURCE may be specified at any one model node. If water quality variables, which are not being simulated by the 1D Water Quality Solver, are specified in SOURCE then the 1D Water Quality Solver will ignore this redundant information.