In Tunisia, during the last two decades, hill lakes occupy an important place in national strategies and Water Conservation Soil (CES). In addition to their role in protecting the environment, hill lakes appear as local water available for agriculture. However, these water infrastructures are quite sensitive to sedimentation due to strong contributions. Water erosion affects nearly 3 million hectares of agricultural land in Tunisia, and is a threat to the sustainability of small dams to mobilize surface waters; where the dominant economic activity remains agriculture. Therefore, control methods are necessary to ensure sustainable land management and secure agricultural production. The objective of this study is to provide evidence for mapping and vulnerability to regionalize multifactor siltation of 26 small lakes located in Central Tunisia, along the Tunisian Dorsal to Cap Bon. The approach involves an analysis of the main factors of erosion: the rainfall erosivity, soil erodibility, slope and land use. The resulting maps are integrated into a Geographic Information System (GIS) using an additive combination to map vulnerability to siltation. This card is validated by field observations. Three classes of multi siltation vulnerability were distinguished: areas with low vulnerability (49.6%); areas with medium vulnerability (27.6%) and highly vulnerable areas (22.8%). This first draft map is a tool to help decision makers for the allocation of crop areas and sites that may contain socio-economic infrastructure on the one hand and used to planning strategies for the development and management of water resources and conservation of water and soil at the scale of small watersheds other.

We proposed in this research to analyze and quantify the evolution of liquid and solid contributions and to study the hydrological behavior of hill lake El Hnach. Watershed El Hnach is located in semi-arid zone of the Tunisian Dorsal (Siliana) , instrumented since 1993, control an area of 385 hectares and a perimeter of 9 Km index overall slope is 0.028, corresponding to strong relief, makes the sensitive watershed erosion. Lake El Hnach had a total initial storage capacity of 77400 m3. This lake has lost 18770 m3, or 24% for a period of 4 years of existence. It loses 6.06 % of the storage capacity per year. According to hydrological analysis, the behavior of El Hnach follows three phases: the first to fall before soil tillage and high wetting, the second spring for soil with vegetation cover and moderately contaminated and the third for low soil moistened with a partially degraded plowing.