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Le lac Sidi Ali est un lac naturel d'altitude (2070-2080 m), sans exutoire superficiel, déterminé par le barrage d'une coulée basaltique. Doté d'un bassin versant apparent de 15,6 km2, il est alimenté par des eaux de ruissellement et par des sources karstiques. Son niveau subit des variations très fortes, annuelles et interannuelles, sous le contrôle des conditions climatiques, et en particulier des pluies et de l'évapotranspiration. Les périodes de sécheresse qui ont marqué les trois dernières décennies, se sont traduites par un abaissement du niveau de près de 7 m. Mais les précipitations abondantes des années 2008-09 et 2009-10 ont provoqué une nette remontée. Une régression multiple d'assez bonne qualité (r = 0,87) lie la variation annuelle du niveau (d'août à août) à différents paramètres (conditions climatiques et niveau initial du lac).
Lake Sidi Ali is a natural lake at high altitude (2070-2080 m), without surface outlet, determined by the dam of a basalt flow. With an apparent catchment of 15.6 km2, it is fed by runoff and karst springs. Its level shows strong annual and interannual variations, depending on weather conditions, particularly rainfall and evapotranspiration. Droughts that have marked the last three decades have resulted in a lowering of about 7 m of the water level. But heavy rainfall that occurred in 2008-09 and 2009-10 caused a marked rise. A multiple regression of sufficient quality (r = 0.87) binds the annual change (from august to august) at differents parameters (weather conditions and initial level of the lake)

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To characterize the evolution of the vegetation cover in the Korifla basin between 1990 and 2018, and subsequently to reconstitute, understand and explain the climatic and anthropogenic phenomena causing these changes, we adopted a methodological approach combining remote sensing techniques, geographic information systems (GIS) and statistical processing. This work consists of multitemporal satellite images at high and low spatial resolution. After the preprocessing and processing operations of these images and the calculation of the spectral indices NDWI (Normalies difference water index), NDVI (Normalies difference vegetation Index) and BI (Brilliance Index), we have developed multi-temporal maps of the vegetation, water and soil. The establishment and processing of land cover maps (LCM) through the use of the “change detection” application has allowed us to quantify the changes in vegetation cover during the last 28 years in the Korifla basin. As a result, the NDVI maps show that the vegetation cover of the Korifla basin suffered a degradation between the 1990s and 2010 against a regeneration between 2010 and 2018. This last increase is not detectable by the SVM method. As for the “change detection” technique, it confirms the regression of the areas of plant cover between 1990 and 2010 followed by an increase between 2010 and 2015 and relayed by a new regression of these areas between 2015 and 2018.