Spatial and temporal variability of rainfall: case of Bizerte-Ichkeul Basin (Northern Tunisia)
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ORIGINAL PAPER
Spatial and temporal variability of rainfall: case of Bizerte-Ichkeul Basin (Northern Tunisia) Hiba Jemai 1 & Manel Ellouze 1 & Habib Abida 1 & Benoit Laignel 2 Received: 13 September 2017 / Accepted: 15 March 2018 # Saudi Society for Geosciences 2018
Abstract This study examines spatial and temporal variability of rainfall in Bizerte-Ichkeul Watershed. The basin, located in the extreme north of Tunisia, covers an area of 3084 km2. Thirteen rainfall stations, with continuous monthly precipitation records over the period (1970–2011), were considered in the analysis. Two methods were used. In the first, the dimensionless standardized precipitation ratio is applied to examine precipitation temporal variation. The second method is represented by continuous wavelet analysis for the precipitation spatial analysis and the identification of the origin of its variability. The study of temporal variability of annual rainfall showed severe persistent and recurrent drought episodes over the period (1977–2001). Wavelet analysis resulted in detecting the modes and origins of precipitation variability. Three energy bands were clearly identified: (1, 2– 4, and 4–8 years) for the entire watershed. The visualization of the power distribution showed that the observed modes of variability are different in their power distributions from one station to another. The approach adopted allowed the identification of two groups with the same precipitation frequency and temporal variation. These groups were defined according to the difference in occurrence of the frequency band for each station. Keywords Bizerte-Ichkeul Basin . Precipitation . Standardized precipitation ratio . Continuous wavelets
Introduction Identifying the impact of climate change on hydrological systems and water resources (greenhouse effect, increase in temperature, reduction of rainfall, etc.) is a major challenge for scientists. Climate change is considered the greatest challenge for coastal areas (Nicholls and Klein 2005; Najjar et al. 2000), forestry (Easterling et al. 2000), and many economic and social sectors such as agriculture (Albert and Shortle 2000) and
* Hiba Jemai [email protected] Manel Ellouze [email protected] Habib Abida [email protected] Benoit Laignel [email protected] 1
Faculty of Sciences of Sfax, Road Sokra, 3000 Sfax, Tunisia
2
UMR CNRS 6143 Continental and Coastal Morphodynamics ‘M2C’ University of Rouen, 76821 Mont-Saint-Aignan Cedex, France
ecosystems (Scavia et al. 2002; Hammer 1999). Several recent large-scale climatic events have pushed the global community to address climate change and understand the irregular distribution of precipitation in space and time (Khoualdia et al. 2014). The results of various studies (from 1991 to 2010) on the evolution of precipitation show that climate change resulted in an intensification of precipitation and a more perceptible recurrence of extreme events (New et al. 2001; Solomon et al. 2007; Planton et al. 2005). Among these studies are those interested in the
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