Etude des techniques et aménagements traditionnels de conservation de l’eau et du sol dans les montagnes du nord algérien

Abstract

Water erosion is the main source of soil degradation in arid and semi-arid areas, particularly in the Mediterranean region. This phenomenon, which affects the soil and water resources of Algerian basins, is linked to many interacting factors. The objective of this study is to analyze and study the phenomenon of water erosion and sediment transport in the semi-arid and Mediterranean context, to conduct this study, we have chosen a typical semi-arid watershed case of wadi El-Ham with an area of 5594 km² and a perimeter of 492 km, it is located north-west of the large basin of Hodna basin (26 000 km²),. This Hodna basin is characterized by both a semi-arid and Mediterranean climatical context, because it is located less than 150 km from the Mediterranean. The availability and reliability of rainfall and hydrometric data were among the criteria for choosing this study area, the basin is equipped with 12 rainfall stations and one gauging station Rocad-sud located at the outlet. of the watershed The use of modern tools and technologies (GIS and remote sensing) has allowed the generation and integration of multiples maps of the different factors of the Universal Soil Loss Equation (RUSLE) to obtain erosion distribution maps. For wadi Elham watershed case, the resulting map shows an average specific degradation of 5.7 (t/ha/year) in the entire watershed. This result is compared to the suspended sediments measured at the Rocade-Sud gauging station located at the outlet watershed. These data consist of 1293 instantaneous measurements of water flow and suspended sediment concentration recorded over 21 years. Through this comparison, the used approach of RUSLE GIS estimates the soil loss at wadi ElHam in the Hodna region of Algeria with a mean relative error of 7.5%. The study showed that water erosion plays an important role in the degradation of natural resources (water and soil), despite the investments made by the Algerian authority to protect these resources. This phenomenon continues and even accelerates; it is still causing enormous damage that is above the tolerable threshold. Part of this thesis work is devoted to the study and analysis of water and soil conservation techniques to complement those carried out in several areas (Wadi El Ham "Msila", Oulhassa "Ain Temouchent "Honaine " Tlemcen "). Water and soil conservation and management strategies are of primary interest, which has enabled us to contribute to the identification of the different techniques for their conservation, and to highlight their effectiveness and relevance . This evaluation demonstrated the positive role of these techniques in water control, the preservation of natural environments and their adaptation to the difficult conditions of dry and semi-arid areas.