What | pi_ratingcurves.xml |
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Description | Configuration for rating curves at specific locations |
schema location | https://fewsdocs.deltares.nl/schemas/version1.0/pi-schemas/pi_ratingcurves.xsd |
The transformation stageDischarge/ratingCurve uses rating curves according to the schema pi_ratingcurves.xsd.
Rating curves can be stored in the folder RegionConfigFiles in the file RegionConfig.xml , or can be imported in the FEWS database with TimeSeriesImport module, import type “pi_ratingcurves”
The schema of the pi-ratingcurves can be found at: https://fewsdocs.deltares.nl/schemas/version1.0/pi-schemas/pi_ratingcurves.xsd
The header element contains the metadata about the rating curve. Below an overview of the available elements.
The table contains the actual description of the Table rating curve.
The slope will be computed as:
The discharge can be calcuted from the stage by using the following equation:
When the logartimic option is selected the slope will be calculated by:
The discharge can be computed by using the following equation:
The stage can be computed by using the following equation:
When an offset is defined the stage can be calculated by:
minStage
The minimum stage which is allowed for this rating curve. If the minStage is configured as 0.2m and a stage of 0.1m is used as input to calculate a discharge.
than the actual stage used in the calculation will not 0.1m but 0.2m. If the rating curve is used in a discharge to stage calculation and the calculated stage is lower than
the minStage than the calculated stage will be set to the minStage value. If, for example, the minStage is set 0.2m and the calculated stage is equal to 0.1m the
actual calculated stage will be corrected to 0.2m to ensure that no stages lower than minStage are calculated.
This option is usually used to limit the stage value calculated when using extrapolation.
maxStage
The maximum stage which is allowed for this rating curve.
If the maxStage is configured as 5.2m and a stage of 5.5m is used as input to calculate a discharge,
then the actual stage used in the calculation will not be 5.5m but 5.2m. If the rating curve is used in a discharge to stage calculation and the calculated stage is higher than
the maxStage than the calculated stage will be set to the maxStage value. If, for example, the maxStage is set 5.2m and the calculated stage is equal to 5.5m the
actual calculated stage will be corrected to 5.2m to ensure that no stages higher than maxStage are calculated. It is possible to configure the maxStage as INF which means that the
maxStage is set to infinite. Which is the same as defining no maximum stage
row
The row element can be used to define the rows of the stage-discharge table. Each row has a mandatory stage and discharge element. An optional offset can be added.
If a row doesn't include an offset element then the previous defined offset will be used.
PowerEquation can be used as PI Rating cuve since Delft-FEWS version 2018.02.
The powerEquation uses the following equations:
discharge = cr * (stage - alpha)^ beta + Q0
stage = (discharge/cr)^(1/beta) + alpha
where ‘cr’ and ‘beta’ are rating curve constants, ‘alpha’ is a constant which represents the stage corresponding to zero discharge and Q0 is optional shifting constant.
To show the stageToDischargePowerEquation rating curves in the TimeSeriesDisplay, a table is generated on the fly from the power equations.
For each equation ten stage values are generated using increment (max stage – min stage) /10 , and for each stage a discharge is computed. Please note that this table is only used in the display and not in TransformationModule computations.