Current Status of Time Series Analysis in Hydrological Sciences - Hydrologic Time Series Analysis: Theory and Practice - page 117

Columbia and the Yukon Territory. On the other hand, in southern Canada,
significant decreases were observed in all percentiles of the daily streamflow
distribution. The breakup of river ice and the ensuing spring freshet occur
significantly especially in British Columbia. The results also suggest earlier
freeze-up of rivers, particularly in eastern Canada. The trends observed in the
hydroclimatic variables in this study are in agreement with those identified in
the climatic variables in other Canadian studies.
Alemaw and Chaoka (2002) investigated possible trends in the annual
riverflow of 502 rivers (data from early 1950s to late 1990s) in the region of
South Africa by visualization technique. The rescaled adjusted partial sums
(RAPS) were used instead of the actual time series plots of runoff. A simulation
experiment of the technique was conducted to demonstrate how the plot of
RAPS offers a reasonable visualization of the readily apparent mode of
underlying trend, which may be hidden in the standard time series plots. The
dominantly visualized trends were linear and declining. A subsequent linear
trend test by fitting a linear trend model to the annual river discharge series
revealed a dominant negative slope ranging from -6.8 to -0.2%; it suggests
the existence of declining trends in some rivers of the South African region.
Of the 502 time series under study, 137 time series had statistically significant
decreasing trend, 96 series had significant increasing trend, and the remaining
269 series had no trend at all.
Birsan et al. (2002) analyzed the mean daily runoff data from undisturbed
and independent watersheds in Switzerland for detecting trends by the Mann-
Kendall trend test. Based on the seasonal analyses of streamflow quantiles, it
was found that: (i) the streamflow has increased in the winter period, especially
the winter annual maximum, at about 60% of the stations; and (ii) the
streamflow has decreased in the summer period, particularly the low streamflow
quantiles. The trends were found to be statistically significant, which indicate
a substantial change in the streamflow regime.
Ramesh and Davison (2002) proposed semi-parametric approaches to
trend analysis using local likelihood fitting of annual maximum and partial
duration series, and demonstrated their application to the exploratory analysis
of changes in extremes in sea level and river flow data. Bootstrap methods
were used to quantify the variability of estimates.
Adeloye and Montaseri (2002) described three tests for determining
consistency, trend, and randomness in hydrological data series. The tests were
then applied to monthly streamflow data records from seven sites — three in
Iran and four in Yorkshire, England. All hydrological series were found
consistent, trend-free and random. Furthermore, few goodness-of-fit tests (i.e.,
Chi-square, Kolmogorov-Smirnov, probability plot correlation coefficient and
moment ratio diagram) for probability distribution are discussed. Based on
the results, probability plot correlation coefficient test was found simple to
use and this test can be employed even if critical test-statistic values are not
known.