Dry weather flow can be generated for sub-areas in the network from pre-defined residential, commercial, and industrial urban areas.


Sewage inflow estimates are made at discrete locations along the trunk sewers of any specified drainage basin. These estimates are calculated from data describing drainage basin subdivisions (referred to as sub-areas) under which the trunk sewer passes. Dry weather flow calculations are unnecessary when modelling separate storm sewers, unless it is desired to generate a base flow with dry weather flow characteristics.

This version of XPSWMM and XPStorm allows one such sub-area per node, so that the predominant land use category loading the trunk sewer must be defined. The model calculates a daily sewage flow and pollutant concentration averaged over the entire year for each sub-area. If study area data is available, the estimates for individual sub-areas are adjusted by a constant fraction to match the total area records. These estimates are adjusted during the simulation by factors that depend on the day of the week and hour of the day, to account for temporal variation.

This dialog allows the definition of these daily and hourly temporal variations, and the total study area data to which estimated sub-area flows will be adjusted by the model to match.

 

Flow Temporal Variation

This dialog allows for the definition of daily and hourly correction factors for the pollutant loads generated from dry weather flow. The pollutant list shown is that defined in the Sanitary or Hydraulics Pollutant Global Database.

Daily Multiplier

Multiplier of the average daily value for the value on a particular day of the week. i.e. the ratio of the daily value to the mean daily value. Typical daily flow variations are shown in the following table:

Day Ratio of Mean Flow
Sunday 0.96
Monday 1.08
Tuesday 1.04
Wednesday 0.92
Thursday 1.03
Friday 1.00
Saturday 0.96 

Hourly Multiplier

Multiplier of the average hourly value for the value on a particular hour in the day. i.e. the ratio of the hourly value to the mean hourly value. A representative hourly flow variation is shown in the following table:

Hour of Day Ratio of Mean Flow
12 am 0.62
1 0.52
2 0.50
3 0.50
4 0.52
5 0.77
6 0.77
7 1.38
8 1.48
9 1.48
10 1.38
11 1.38
12 noon 1.35
1 pm 1.30
2 1.30
3 1.20
41.20
5 1.10
6 1.10
7 0.95
8 0.95
9 0.80
10 0.80
11 0.60

Pollutant Temporal Variation

This button allows for the definition of daily and hourly correction factors for the pollutant loads generated from dry weather flow. The pollutant list shown is that defined in the Sanitary or Hydraulics Pollutant Global Database.

 


Daily Multiplier

Multiplier of the average daily value for the value on a particular day of the week. i.e. the ratio of the daily value to the mean daily value. Typical daily flow variations are shown in the following table:

Day Ratio of Mean Flow
Sunday 0.96
Monday 1.08
Tuesday 1.04
Wednesday 0.92
Thursday 1.03
Friday 1.00
Saturday 0.96 


Hourly Multiplier

Multiplier of the average hourly value for the value on a particular hour in the day. i.e. the ratio of the hourly value to the mean hourly value. A representative hourly flow variation is shown in the following table:


Hour of DayRatio of Mean Flow
12 am0.62
10.52
20.50
30.50
40.52
50.77
60.77
71.38
81.48
91.48
101.38
111.38
12 noon1.35
1 pm1.30
21.30
31.20
41.20
51.10
61.10
70.95
80.95
90.80
100.80
110.60


Study Area Data

This button allows the definition of certain adjustment factors used in calculation of individual sub-area dry-weather flow contributions.

Total Population

The total population in all sub-areas, in thousands.

Consumer Price Index

The current consumer price index, where a value of 100 corresponds to the year 1963. This index is used to adjust water price used in estimations of water use for residential areas.

Composite Construction Cost Index

The composite construction cost index, relative to an index of 100 for the year 1960. This index is used to adjust house valuations used in the estimation of dry weather flows from residential areas.

Simulation Start Week Day

The day of the week at which simulation is to begin. The day ranges from 1 to 7, with Sunday being day number 1. This parameter is required to synchronize the appropriate day in the temporal patterns for flow and pollutant load to the simulation.

Study Area Flow and Loads

These options control how study area flows and load data are used to adjust sub-area flows in the generation of dry weather flow. If the Use Default Data option is selected default values for average dry weather flows and pollutant concentrations are used to calculate individual sub-area contributions, otherwise further Measured data describing the total study area will be required.

Use Default Rates

If data is not available to adequately define the total watershed study area the default rates should be used to generate the dry weather flow.

 

Domestic Flow (Wastewater Flow per Capita)

The total study area average sewage flow per capita, cfs [cms]. This value would typically be obtained from treatment plant records and is used in the conversion of loads based on population to concentrations.

Infiltration Allowance (Flow per Capita)

The total study area average infiltration flow per capita, cfs [cms]. This value plus the wastewater flow is used to define the total dry weather flow.

Pollutant

These are the pollutants as selected in the 'Pollutant List' item in Job Control.

Rate

Study Area Pollutant Rate. The rate is given in units consistent with the pollutant, as defined in the Pollutants Global Database. The rate will be a concentration if the pollutant is defined to use volume or a per capita rate if the pollutant is defined in terms of population. Typical values are:

E-COLI 200 *10^9 MPN per capita per day

SS 263 mg /l

BOD 241 mg/l

Use Measurements

This dialog deals with data required for the total study area, if records are available to be used in estimating sewage quality. This data is used to derive the dry-weather flows from the entire area under study. Contributions from individual sub-areas are adjusted by the model to match these values.

 Firstly, the average daily values of flow and pollutant concentrations are used to calculate the total loads of pollutant for the study area. Infiltration (computed by the model) is then subtracted from the daily average flow. Next, the known process flow contributions (defined locally at nodes) are deducted from the daily totals, yielding further corrected characteristics. Loads are then corrected for personal income variations, degree of commercial use, garbage grinder usage, and population. Average concentrations of all pollutants are then computed. These values are used as the basis for adjusting sub-area concentrations.

  

Industrial Area

The total contributing Industrial area, acres [ha].

Commercial Area

The total contributing Commercial area, acres [ha].\

Parkland Area

The total area of park and open space within the study area, acres [ha].

Total Area

The total area of the study area, acres [ha]. This is the total watershed area being divided into sub-areas at nodes.

High Income Area

The total contributing residential area where the household income is above $15,000 (in 1963 dollars), in acres [ha].

Average Income Area

The total contributing residential area where the household income is above $7,000 but below $15,000 (in 1963 dollars), in acres [ha].

Low Income Area

The total contributing residential area where the household income is below $7,000 (in 1963 dollars), in acres [ha].

Garbage Grinder Area

The total residential area that contributes additional waste from garbage grinders, in acres [ha].

Total Study Area (Study Area Process Flow)

This dialog provides for the entry of measured flows and pollutant concentrations for the total study area. These values are used as a basis for adjusting calculated dry-weather flows from sub-areas.

  

Study Area Flow

The total study area average sewage flow, cfs [cms]. This value would typically be obtained from treatment plant records.

Pollutant

These are the pollutants as selected in the 'Pollutant List' item in Job Control.

Concentration

Study Area Pollutant Concentration. The concentration is given in units consistent with the pollutant, as defined in the Pollutants Global Database.