General Description

Initialize self. See help(type(self)) for accurate signature. API Reference

Attributes

Example

coming soon...

{

}

General Description

A simple parameter defining a constant value. API Reference

Attributes

Example

{
    type: 'constantparameter',
    value: 123
}

General Description

Parameter which provides a daily profile.

The daily profile returns a different value based on the month of the current time-step.

Attributes

Example

General Description

A collection of IndexParameters

This class behaves like a set. Parameters can be added or removed from it. Its index is the index of it’s child parameters aggregated using a aggregating function (e.g. sum). API Reference

Attributes

Example

coming soon...

{

}

General Description

A collection of IndexParameters. This class behaves like a set. Parameters can be added or removed from it. It’s value is the value of it’s child parameters aggregated using a aggregating function (e.g. sum). API Reference

Attributes

Example

{
	"type": "AggregatedParameter",
	"agg_func": "product",
	"parameters": [
		"Baseline demand",
		"Control curve demand factor"
	]
}

In this case Aggregated Parameter is multipliying two parameters togther

• Baseline demand

• Control curve demand factor

This example shows a Baseline demand being multiplied by a factor that reduces demand based on a reservoir control curve. You can click on the each of these Parameters to see how they are defined.

All the Parameter subclasses in pywr are descended from a common base class.

General Description

Base parameter providing an index method.

Attributes

Example

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General Description

Parameter that takes negative of another Parameter.

Attributes

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General Description

A Scenario varying Parameter. The values in this parameter are constant in time, but vary within a single Scenario.

Attributes

Example

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General Description

A Scenario varying IndexParameter. The values in this parameter are constant in time, but vary within a single Scenario.

Attributes

Example

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Paramters are functions that return a value in the model at each time-step. These values can be a constant, based on time (e.g., on the day or month), a calculation based on the time step's reservoir storage and many other calculations. Custom parameter can also be written in Python.

This page describes (most of) the parameter types supported by Pywr. An overview of parameters in Pywr can be found . The full list of built-in Pywr parameters are found .

1. Creating a Parameter

In a Network, click the 'Parameters' Tab:

Next to the 'Parameters-Type Categories' section, click the '+' button and select 'PYWR_PARAMETER'.

A text-input will appear. Enter the name of your parameter:

Modify the parameter as required in the JSON editor provided:

2. Parameter editors in WaterStrategy

To make parameter modifications simpler, WaterStrategy offers editors for commonly used Parameters, such as Monthly Profile parameters, with pre-populated default values, and graphical editors to make entering of data simpler.

Example parameter editor

In the Parameters Tab, when adding a new Parameter, select 'PYWR_PARAMETER_MONTHLY_PROFILE' as shown:

Note that the edior which appears will show a JSON tab, but also a Plot and Table tab. Modifying the data in the table will automaticall update the data in the JSON as shown:

These changes automatically update the JSON:

General Description

Parameter that takes maximum of another Parameter and constant value (threshold).

This class is a more efficient version of AggregatedParameter where a single Parameter is compared to constant value. API Reference

Attributes

Example

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{

}

General Description

The weekly profile contains 52 weeks per year. The last week of the year will have more than 7 days, as 365 / 7 is not whole. API Reference

Attributes

Example

{
    type: 'weeklyprofile',
    values: [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 ... ]
}

General Description

Parameter that takes maximum of the negative of a Parameter and constant value (threshold). API Reference

Attributes

Example

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{

}

General Description

Parameter that divides one Parameter by another. API Reference

Attributes

Example

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{

}

General Description

Parameter that takes minimum of another Parameter and constant value (threshold).

This class is a more efficient version of AggregatedParameter where a single Parameter is compared to constant value. API Reference

Attributes

Example

coming soon...

{

}

General Description

Parameter which provides a daily profile per scenario.

This parameter provides a repeating annual profile with a daily resolution. A different profile is returned for each member of a given scenario.

Attributes

Example

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General Description

Parameter that offsets another Parameter by a constant value.

This class is a more efficient version of AggregatedParameter where a single Parameter is offset by a constant value.

Attributes

Example

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General Description

Parameter that provides a weekly profile per scenario

This parameter provides a repeating annual profile with a weekly resolution. A different profile is returned for each member of a given scenario.

Attributes

Example

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General Description

Time varying parameter using an array and Timestep.index with multiplicative factors per Scenario.

Values is the baseline timeseries data that is perturbed by a factor. The factor is taken from factors which is shape (scenario.size, 12). Therefore factors vary with the individual scenarios in scenario and month.

Attributes

Example

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General Description

Parameter that provides a monthly profile per scenario.

Behaviour is the same as MonthlyProfileParameter except a different profile is returned for each ensemble in a given scenario.

Attributes

Example

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General Description

Parameter that takes minimum of the negative of a Parameter and constant value (threshold). API Reference

Attributes

Example

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{

}

General Description

Parameter which provides a uniformly reducing value from one to zero.

This parameter is intended to be used with an AnnualVirtualStorage node to provide a profile that represents perfect average utilisation of the annual volume. It returns a value of 1 on the reset day, and subsequently reduces by 1/366 every day afterward. API Reference

Attributes

Example

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{

}

General Description

Parameter which interpolates a daily profile using a radial basis function (RBF).

The daily profile is computed during model reset using a radial basis function with day-of-year as the independent variables. The days of the year are defined by the user alongside the values to use on each of those days for the interpolation. The first day of the years should always be one, and its value is repeated as the 366th value. In addition the second and penultimate values are mirrored to encourage a consistent gradient to appear across the boundary. The RBF calculations are undertaken using the scipy.interpolate.Rbf object, please refer to Scipy’s documentation for more information. API Reference

Attributes

Example

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{

}

General Description

Time varying parameter using an array and Timestep.index

The values in this parameter are constant across all scenarios. API Reference

Attributes

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{

}

General Description

Base class for parameters returning one of two values depending on other state. API Reference

Attributes

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{

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General Description

Returns one of two values depending on the year of the current timestep. API Reference

Attributes

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{

}

General Description

Parameter which uses an IndexParameter to index an array of Parameters.

An example use of this parameter is to return a demand saving factor (as a float) based on the current demand saving level (calculated by an IndexParameter). API Reference

Attributes

Example

{
	"type": "indexedarrayparameter",
	"index_parameter": "Reservoir control curve",
	"params": [
		1,
		0.9,
		0.8,
		0.5
	]
}

The above code uses the Index supplied by the parameter called 'Reservoir control curve', which is a Control Curve Index Parameter. Index 0 returns a 1, Index 2 returns 0.9 etc...

In this example this parameter is used to reduce a demand based on a reservoir control curve. Please go to the Aggregated Parameter example to see how this is done.

Please see how the Reservoir control curve parameter is defined.

General Description

A Scenario varying Parameter.

The values in this parameter are vary in time based on index and vary within a single Scenario. API Reference

Attributes

Example

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{

}

General Description

Returns one of two values depending on current volume in a Storage node. API Reference

Attributes

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{

}

General Description

Returns one of two values depending on the value of a Parameter. API Reference

Attributes

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{

}

General Description

Timeseries parameter with automatic alignment and resampling. API Reference

Attributes

Example

{
	"type": "DataFrameParameter",
	"url": "Inflows_mm3_day.csv",
	"column": "Catchment River 1",
	"index_col": "timestep",
	"parse_dates": true
}

General Description

Parameter which provides a monthly profile. The monthly profile returns a different value based on the month of the current time-step. API Reference

Attributes

Example

{
    type: 'monthlyprofile',
    values: [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1]
}

Water Strategy offers an alternative way to work with Monthly Profiles.

General Description

This Parameter reads array data from a PyTables HDF database.

The parameter reads data using the PyTables array interface and therefore does not require loading the entire dataset in to memory. This is useful for large model runs. API Reference

By storing HDF5 files in the "fixed" format, users can achieve optimal data access speeds, making HDF5 an effective tool for Pywr-scenarios that use DataFrames as parameters, where fast data retrieval is crucial. HDF5 files are read as a dictionary, where each key represents a pandas DataFrame. For example, the structure of an inflows.h5 file might contain three keys, each representing a different river. Each key holds three time series that can be assigned to a Pywr scenario of size 3.

If using h5 file DataFrame for running pywr-scenarios, please refer to pywr-scenarios section in order to activate this feature

Note: The size of pywr-scenarios must match the number of keys in the h5 file

Attributes

Example

{
	"key": "Catchment River 1",
	"scenario": "Climate Change",
	"type": "DataFrameParameter",
	"url": "inflows.h5",
	"index_col": "timestep",
	"parse_dates": true
}

General Description

Returns one of two values depending on a Recorder value and a threshold.

Attributes

Example

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General Description

Returns one of two values depending on previous flow in a node.

Attributes

Example

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General Description

Returns one of two values depending on the ordinal of the current timestep.

Attributes

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General Description

Generic interpolation parameter that uses a node’s flow at the previous time-step for interpolation.

Attributes

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General Description

Parameter value is equal to the interpolation of another parameter.

Attributes

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General Description

Base class for all Parameters that rely on a the attached Node containing a control_curve Parameter.

Attributes

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General Description

The hydropower target parameter is a parameter that returns flow from a hydropower generation target. This parameter calculates the flow required to generate a particular hydropower production target. It is intended to be used on a node representing a turbine where a particular production target is required each time-step. API Reference

Attributes

Example

{

}

General Description

Parameter track the deficit (max_flow - actual flow) of a Node. API Reference

Notes: This parameter is a little unusual in that it’s value is calculated during the after method, not calc_values. It is intended to be used in combination with a recorder (e.g. NumpyArrayNodeRecorder) to record the deficit ( defined as requested - actual flow) at a node. Note that this means recording this parameter does not give you the value that was used by the solver in this timestep. Alternatively, this parameter can be used in the model by other parameters and will evaluate to yesterdays deficit, where the deficit in the zeroth timestep is zero.

Attributes

Example

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{

}

General Description

Parameter value is equal to the quadrature of the interpolation of another parameter. API Reference

Attributes

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{

}

General Description

A control curve Parameter that interpolates between three or more values.

Return values are linearly interpolated between control curves, with the first and last value being 100% and 0% respectively. API Reference

Attributes

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{

}

General Description

A control curve Parameter that interpolates between two or more pairs of values.

Return values are linearly interpolated between a pair of values depending on the current storage. The first pair is used between maximum and the first control curve, the next pair between the first control curve and second control curve, and so on until the last pair is used between the last control curve and the minimum value. The first value in each pair is the value at the upper position, and the second the value at the lower position. API Reference

Attributes

Example

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{

}

General Description

Parameter that returns the current discount factor based on discount rate and a base year. API Reference

Attributes

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{

}

General Description

Parameter that integrates a piecewise function.

This parameter calculates the integral of a piecewise function. The piecewise function is given as two arrays (x and y) and is assumed to start from (0, 0). The values of x should be monotonically increasing and greater than zero. API Reference

Attributes

Example

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{

}

General Description

Parameter that returns the delayed flow for a node after a given number of timesteps or days. API Reference

Attributes

Example

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{

}

Example

{
	"type": "controlcurveindexparameter",
	"storage_node": "Reservoir name",
	"control_curves": [
		{
			"type": "monthlyprofileparameter",
			"values": [
				0.45,
				0.45,
			  	0.45,
				0.45,
				0.45,
				0.45,
				0.45,
				0.45,
				0.45,
				0.45,
				0.6,
				0.6
				]
		},
		{
			"type": "constant",
			"value": 0.4
		},		
		{
			"type": "constant",
			"value": 0.1
		}		
	]
}

The above code defines 3 reservoir control curves for the reservoir called "Reservoir name". It returns an Index depending on how full the reservoir is:

To see how this index is used with an Indexed Array Parameter click here.

General Description

Generic interpolation parameter that returns a value based on a Reservoir or Storage nodes current (time step) volume. The

parameter uses an array (table) of Reservoir Volumes and corresponding values. In this case the associated values are the corresponding Reservoir Area for a given Volume.

Interpolation is used to calculate values betwen points given in the interpolation array. API Reference

Attributes

Example

The following Json shows an example Area vs Volume rating cure for a reservoir. This could be used to define the Area attribute of a Storage or Reservoir node.

{
  "type": "InterpolatedVolumeParameter",
  "node": "Reservoir or Storage node name",
	"volumes": [
		0,
		7,
		10,
		15,
		25
	],
	"values": [
		1,
		2,
		4,
		6,
		14
	],

	"interp_kwargs": {
		"kind": "linear"
	},
  "comment": "volumes: Mm3, values:  Km2"
}

The Json represents the table below:

When plotted it looks like this:

Below is an example Area rating table

When plotted it looks like this

General Description

Parameter that utilises a different child parameter in each scenario ensemble.

This parameter is used to switch between different child parameters based on different ensembles in a given Scenario. It can be used to vary data in a non-scenario aware parameter type across multiple scenario ensembles. For example, many of control curve or interpolation parameters do not explicitly support scenarios. This parameter can be used to test multiple control curve definitions as part of a single simulation. API Reference

Attributes

Example

coming soon...

{

}

General Description

Parameter that provides the flow from a node from the previous time-step. API Reference

Notes: This parameter keeps track of the previous time step’s flow on the given node. These values can be used in calculations for the current timestep as though this was any other parameter.

Attributes

Example

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{

}

General Description

A Parameter which returns the value from an annual harmonic series.

This Parameter comprises a series N cosine function with a period of 365 days. The calculation is performed using the Julien day of the year minus 1. This causes a small discontinuity in non-leap years. API Reference

$f(t)=A+∑n=1NAn⋅cos((2πnt)/365+ϕn)$

Attributes

Example

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{

}