干旱区生态环境知识资源中心

Since 1994, a hill reservoirs hydrological monitoring pilot network has been established and monitored in the Tunisian Dorsal by the General Directorate of Agriculture Land Management and Conservation (DG/ACTA) and the Research Institute for Development (IRD). The aim of this network is to study the hydrological and erosion behaviour of small watersheds. These structures have very diverse impluviums from a semi-forest area to more or less anthropized to a landscape totally devoted to agricultural activities. These small watersheds with an areas range between 1.6 and 18 km(2) are the most representative for the semi-arid rainfall gradient ranging from 250 to 600 mm of interannual precipitation. The basic purpose of this study was to understand the overall functioning of watersheds and to deduce the characteristics that could contribute to the development and management of these hydraulic structures, considering basic knowledge of soil type and morphological and anthropogenic characteristics of watersheds. The first criterion to consider is the topography or the average slope of the catchment. The second criterion is the lithology with the cover of marls and clays on the watershed. The two other criteria are anthropogenic: the first is the percentage of the area covered by cultivated soils and the second is the percentage of the area covered by anti-erosive techniques or forests. Thus, with the creation of hill reservoirs, for small irrigation water supply, a limitation in the expansion of anti-erosion techniques should be considered to ensure regular water supply from the reservoir.