Current Status of Time Series Analysis in Hydrological Sciences - Hydrologic Time Series Analysis: Theory and Practice - page 105

Brunetti et al. (2000) analyzed the daily precipitation data of northern
Italy for trend detection. The nonparametric Mann-Kendall test was applied to
the mean anomaly series of some precipitation intensity statistics over five
stations: Genoa (1833-1998), Milan (1858-1998), Mantova (1868-1997),
Bologna (1879-1998) and Ferrara (1879-1996). It was found that in northern
Italy, the number of rainy days has a more significant negative trend than the
corresponding precipitation amount. Consequently, the precipitation intensity
has a positive trend. The increase in precipitation intensity was found to cause
a significant positive trend in the total precipitation contributed by heavy
precipitation events (i.e., daily precipitations >25 mm and >50 mm).
Furthermore, the trend was mainly caused by past 60-80 years, and was
particularly evident during the periods of 1930-1945 and 1975-1995.
Molénat et al. (2000) analyzed the hydrological and hydrochemical
behaviour of three agricultural catchments located in different regions of
France (Kervidy, Melarchez and Mercube). The time series were considered
as input or output data and the spectral analysis was performed. The input data
for hydrology and chemistry were respectively rainfall and nitrate leaching,
and the output data were streamflow and nitrate concentration in the stream.
It appears that nitrate concentrations measured at the outlet of the three
catchments exhibit a strong and unique one-year periodicity. This periodicity
is due to the hydrological regime and the time distribution of the nitrate
availability in the soil. Moreover, a cross-spectral analysis was performed
between the input and output data for each catchment and the major processes
that govern water and nitrate transfer and the characteristic time scale of these
processes were identified. It was concluded that the spectral and cross-spectral
methods are valuable techniques for identifying the main transfer processes
operating in different catchments.
Sharma et al. (2000) studied basinwide land-use, climatic and hydrologic
trends over the Kosi Basin (54,000 km 2 ) in the central Himalayan region. The
analysis of anthropogenic inputs showed that the population of the basin has
increased at a compound rate of about 1% per annum during past four decades.
A comparison of the land-use data of the 1960s and 1978-1979 did not reveal
noticeable trends in the land-use change. On the other hand, the analysis of the
meteorological and hydrological time series from 1947 to 1993 indicated an
increasing tendency of temperature and precipitation. However, the statistical
tests of hydrologic trends indicated an overall decrease in the discharges of
the Kosi River and its major tributaries. The decreasing trends of streamflow
were found more significant during low-flow months. Further, the statistical
analysis of homogeneity suggested that the climatic as well as the hydrologic
trends are more localized in nature and do not have a distinct basinwide
significance.
Brunetti et al. (2001) analyzed the seasonal and annual precipitations and
the number of rainy days in northeastern Italy during 1920-1998. The
precipitation intensity was analyzed by using both the mean precipitation