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| Titel |
Record extension for short-gauged water quality parameters using a newly proposed robust version of the Line of Organic Correlation technique |
| VerfasserIn |
B. Khalil, J. Adamowski |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 16, no. 7 ; Nr. 16, no. 7 (2012-07-23), S.2253-2266 |
| Datensatznummer |
250013377
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| Publikation (Nr.) |
 copernicus.org/hess-16-2253-2012.pdf |
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| Zusammenfassung |
| In many situations the extension of hydrological or water quality time
series at short-gauged stations is required. Ordinary least squares
regression (OLS) of any hydrological or water quality variable is a
traditional and commonly used record extension technique. However, OLS tends
to underestimate the variance in the extended records, which leads to
underestimation of high percentiles and overestimation of low percentiles,
given that the data are normally distributed. The development of the line of
organic correlation (LOC) technique is aimed at correcting this bias. On the
other hand, the Kendall-Theil robust line (KTRL) method has been proposed as
an analogue of OLS with the advantage of being robust in the presence of
outliers. Given that water quality data are characterised by the presence of
outliers, positive skewness and non-normal distribution of data, a robust
record extension technique is more appropriate. In this paper, four
record-extension techniques are described, and their properties are
explored. These techniques are OLS, LOC, KTRL and a new technique proposed
in this paper, the robust line of organic correlation technique (RLOC). RLOC
includes the advantage of the LOC in reducing the bias in estimating the
variance, but at the same time it is also robust in the presence of outliers.
A Monte Carlo study and empirical experiment were conducted to
examine the four techniques for the accuracy and precision of the estimate
of statistical moments and over the full range of percentiles. Results of
the Monte Carlo study showed that the OLS and KTRL techniques have serious
deficiencies as record-extension techniques, while the LOC and RLOC
techniques are nearly similar. However, RLOC outperforms OLS, KTRL and LOC
when using real water quality records. |
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