Versions Compared

Old Version 37

changes.mady.by.user Klaas-Jan van Heeringen

Saved on

compared with

New Version 38

changes.mady.by.user Erik de Rooij

Saved on

Key

  • This line was added.
  • This line was removed.
  • Formatting was changed.

...

Code Block
xml
xml
		<statisticalFunction function="showLowsBelow"/>
		<statisticalFunction function="showPeaksAbove"/>

Double Mass curve

Isused in the study of the consistency and long-term trend test of hydrometeo--rological data. This method was first used to analyze the consistency of precipitation data in Susquehanna watershed United States by Merriam at 1937 (Merriam, 1937), and Searcy made a theoretical explanation

of it (Searcy, et al., 1960). The theory of the double-mass curve is based on the fact that a plot of the two cumulative quantities during the same period exhibits a straight line so long as the proportionality between the two remains unchanged, and the slope of the line represents the proportionality. This method can smooth a time series and suppress random elements in the series, and thus show the main trends of the time series. In recent 30 years, Chinese scholars analyzed the effect of soil and water conservation measures and land use/ cover changes on runoff and sediment using double mass curve method, and have achieved good results (Mu, et al., 2010). In this study, double-mass curves of precipitation vs streamflow and precipitation vs sediment are plotted for the two contrastive periods to estimate changes in regression slope (proportionality) to quantify the overall efficiency of soil conservation measures before and after transition years.
An example of the doubleMassCurve plot is given here:
Image Added

Config example:

Code Block
xml
xml
<statisticalFunction function="doubleMassCurve">
	<dateFormat>yyyy-MM-dd hh:mm</dateFormat>
</statisticalFunction>

 

Duration curve

A convenient way to show the variation of hydrological quantities through time may be done by means of duration curves. For the selected time period the values of the selected quantity are sorted descending (durationExceedence) or ascending (durationNonExceedence). When the duration curve is plotted in the timeseries display, the x-axis will show the entire length in time of the selected view period. Percentages are shown as duration with respect to the entire chosen view period.

...