Information

Transformation:

MergedRatingCurves

Transformation Group:

DischargeStage

Description:

Merges two rating curves using a time dependent weight variable and uses the resulting rating curve to convert discharge input values to stage output values. For each timeStep in the output time series, first the specified two rating curves are merged using the value of the weight input time series at that timeStep. If weight is 1, then uses the first rating curve. If weight is 0, then uses the second rating curve. If weight is between 0 and 1, then interpolates linearly between the first and the second rating curve to get the merged rating curve. Then the merged rating curve is used to convert the discharge input value for that timeStep to a stage output value. This can only use rating curves that are stored as time series in the dataStore. This uses the inverse of the equation Q_output = weight*Q_ratingCurve1(H_input) + (1 - weight)*Q_ratingCurve2(H_input)

Hydrological Information

Purpose and use of Transformation:

This can be used e.g. for a river reach with a lot of vegetation in the summer resulting in a higher hydraulic roughness. Then, you might want to handle a rating curve for the winter period (level of 1m corresponds to 5 m3/s) and one for the summer (same water level represents only 3 m3/s due to the higher roughness). The weight value can be used for shifting inbetween: weight=0 for the winter, weight=1 for the summer, and a weight value of 0.5 for a certain time in spring when vegetation is growing.

Background and Exceptions:

Weight value must always be in the range 0 <= weight <= 1. If ratingCurve(s) not found, then logs a warning message and sets the output to missing values.

Input

discharge input variable with discharge (water flow) values.
weight input variable with weight values.

ratingCurve

References to two rating curves that are merged and used to convert discharge to stage values for this transformation. This can only use rating curves that are stored as time series in the dataStore. To import ratingCurves into the dataStore use timeSeriesImport module with importType pi_ratingcurves to import a file in the pi_ratingcurves.xsd format. The ratingCurves are referenced using their locationId and qualifierId. If no locationId is specified, then the locationId of the stage input variable is used.

Output

stage output variable with stage (water level) values.

Configuration Example

<transformation id="discharge stage merged rating curves test">
	<dischargeStage>
		<mergedRatingCurves>
			<discharge>
				<variableId>input</variableId>
			</discharge>
			<weight>
				<variableId>eta</variableId>
			</weight>
			<ratingCurve>
				<locationId>H-2001</locationId>
				<qualifierId>winterRatingCurve</qualifierId>
			</ratingCurve>
			<ratingCurve>
				<locationId>H-2001</locationId>
				<qualifierId>summerRatingCurve</qualifierId>
			</ratingCurve>
			<stage>
				<variableId>output</variableId>
			</stage>
		</mergedRatingCurves>
	</dischargeStage>
</transformation>
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