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Scale
Implemented at the site scale.
Principal developer
eWater CRC
Scientific Provenance
Providing a pattern of monthly demands as input data is a basic, and well established, approach in river and water supply system, and storage behaviour modelling.
Version
Source version 2.17.
Dependencies
A Water User node is required by Source to access the monthly demand pattern node.
Theory
The monthly demand pattern is input as a set of 12 values of monthly volumes expected to be delivered at the demand node (see Parameters or settings). When a model time-step of less than one month is being used (eg daily) the value for a given month is distributed evenly across all time-steps in that month.
The Monthly Demand node provides a demand value to the Water User node at every model time-step. When modelling a regulated system, the Water User node supplies the Monthly Demand node with a value of maximum travel time (expressed in numbers of model time-steps). At a given model time-step, the demand value provided is the one for the appropriate number of time-steps in advance of the current time-step. When modelling an unregulated system, the demand value provided is the one that is applicable to the current model time-step. More information on how this value is further processed is available in the section of this Scientific Reference Guide.
Assumptions and Limitation
The key assumption is that the demands to be modelled can be adequately represented by a fixed monthly pattern. Amongst other things, while seasonal variations are represented, this assumes the demand in any given month does not change from year to year due to climate variability.
Input data
A fixed pattern of 12 monthly values is input. More information on this and other input data is given in Parameters or settings, below. Full details are provided in the Source User Guide.
Parameters or settings
Model parameters are summarised in Table 31.
Output data
Output comprises a time series of flows.
Table 31. Model parameters
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Parameter
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Description
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Units
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Default
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Range
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Travel time (only when modelling a regulated system)
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Expected time for water to travel from nominated storage to the demand node
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Days
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0
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Governed by maximum travel time in the system being modelled
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Monthly demand values (12 expected)
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A file of demand values
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ML/month
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0.0
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Positive number
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Information from an existing scenario
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An expression defined by the modeller
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Return Flow (see note below)
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Percentage of volume of water supplied (which may differ from demand)
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%
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A fixed volume
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ML/month
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A volume defined using an expression
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ML/month
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allows you to specify a demand as monthly values in megalitres. This is a simple representation supporting the needs of demand and supply analysis. The demand from nodes is accumulated in a bottom-up pass to the identified supply storage, from which water is released (if possible) at the appropriate time to meet the demand. You can configure the model by right-clicking Demand Models and choosing Monthly Pattern from the contextual menu (Figure 1).
Demand can be specified as either:
- Monthly values in the Order per month fields when Annual Total checkbox is not ticked and the column of Order Per Mon in Figure1 will be active; or
- As a percentage of a total amount. Enable the Use Annual Total checkbox and specify the total demand in the respective field. You can then specify what percentage and share of this total amount to allocate each month.
The demands from the two above methods are independent.
You can enter monthly demand values directly or load the data from a comma-separated (.CSV) file (format shown in Table 1). For simulation over smaller time-steps, the monthly volume is evenly distributed across the time-steps for that month.
Note that the order value and percentage value in Table 1 are not related to each other. Source outputs both values in the system to the CSV file regardless the current option (i.e., Order per month or Percentage of Annual Total), and inputs both values in the CSV file to the system as well. However, Source allows importing a single parameter from the CSV file to the system based on the parameter title (i.e. Value or Proportion) if the CSV file only includes one parameter and another parameter in the system will be set up as zero.
| Info | ||
|---|---|---|
| ||
| Note: For a monthly pattern demand model, orders are in units of ML, and are averaged over an entire month for a daily value. To ensure that there is no discrepancy in orders between leap and non-leap years, define a time series demand model with a function as the input data source. Refer to the Time Series Demand model for more information. |
Refer to Return flows for configuring Return flows in the model.
Figure 1. Water User node (Monthly Pattern, Demand)
Table 1. Water User node (Monthly Pattern, data file format)
Row | Column (comma-separated) | ||
|---|---|---|---|
1 | 2 | 3 | |
1 | Month | Value | Proportion |
2 | month | order | percentage |
Where:
month is the first three characters of the month name with a leading capital letter (eg "Jan")
order is the order in megalitres for the corresponding month.
percentage is the percentage of Annual Total value (%) for the corresponding month. It is only related to the Annual Total (ML).