Abstract:
The growth in water needs is through rapid population change, industrial
development and extension of agriculture. Northern Algeria experienced variability in annual
rainfall during the 20th century. This variability was particularly accentuated from the 1980s
and had significant negative impacts on surface water resources, as well as on the rainfall
cycle. Our study consists in characterizing the temporal and spatial variability of the
chronological series of hydro-climatic parameters (rainfall, flows) at the level of four
watersheds of the Highlands of Constantine. ; (Madher, Chemora, Boulefreiss and Foum el
Gueiss basins) for 43 years (1969-2012). A preliminary analysis of all the physical and
geographical parameters of the selected watersheds was carried out. Then, using statistical
trend tests and correlation and spectral analyzes, either increasing or decreasing trends in
temperature, precipitation and flow were observed. A better understanding of the relationship
between climate change and its impacts on the availability of water resources requires an
analysis of trends on series of temperatures, precipitations and flows. This is what we have
done, over a long period, for the basins. The results of this evaluation show a significant
decrease in annual precipitation ranging from 19 to 54.8% and an increase in average
temperature of 0.7 °C at over the past 20 years. This has enabled us to specify the evolution of
rainfall over the past decades and the trends that can be detected there. The break detection
study made it possible to locate a change in the rainfall regime for most of the rainfall stations
studied. The application of the statistical tests to the seasonal rains, allowed us to conclude
that it was the winter and spring rains that recorded a break in the time series. On a monthly
basis, we noticed that it was the months of the two rainy seasons that recorded the most
significant and most significant decreases, especially the months of: December, January,
March and April. The hydrological study, which is based on the statistical processing of
hydrometric data, shed light on the fundamental aspects of annual and seasonal flow, and
therefore of surface water resources and their variability. The values of the coefficients of
variation of the internal intakes are relatively high, which indicates an irregular regime. This
irregularity is more acute in the east. In terms of hydraulics, these wadis are characterized by
a violent and rapid flow. Finally, we looked for the links between this rainfall and
hydrological variability with climatic fluctuations materialized by different climatic indices,
NAO, MO.The study approach is based on the statistical treatment of time series linked to
spatiotemporal dimensions by the method of spectral analyzes adapted to the study of
stationary processes (continuous wavelet analysis, wavelet coherence analysis).
