In this paper, we quantify the water balance of Jessour at the scale of agricultural plots. Jessour (plural of Jesr) are ancestral hydro-agricultural systems in the Dahar plateau (southeastern Tunisia). They consist of small dams built across wadis and gullies, which retain rainwater and sediments, hence enabling cropping. Despite arid climate conditions, Jessour allow the culture of the olive tree beyond its ecological limits. Weather monitoring stations were set up and soil moisture sensors installed down to a depth of 1.25 m in the soil in two neighboring gullies in the village of Zammour: one with a Jesr and one without. Laser granulometry and organic matter analyses were carried out on samples collected near the soil moisture sensors. Measurements were recorded from 28 September 2017 to 21 September 2018. From 10 to 12 November 2017, the region received 123.3 mm rainfall. The Jesr retained the equivalent of 410.3 mm of soil moisture to a depth of 1.25 m whereas the value in the gully was 224.6 mm. Throughout the summer of 2018, the soil available water capacity (AWC) remained above 55 mm in the Jesr, while it dropped to zero in the gully. Jessour are thus very suitable hydro-agricultural systems to face the climate changes concerning this fragile region, located in the transition zone between the semi-arid to arid Mediterranean region and the Sahara.

Weather parameters and soil moisture profiles were measured at an hourly time step during four agricultural years (September to October, from 2018–19 to 2021–22) in two Jessour (water harvesting cultivated terraces) of the same valley in Zmerten (southeastern Tunisia), characterized by an arid climate. One instrumented Jesr (singular of Jessour) was located upstream and the other one downstream. During each dry season, when crops experience water stress, the downstream Jesr had a higher available water content than the upstream one; in the downstream Jesr the soil profile moisture remained above the wilting point, whereas in the upstream soil surface, moisture levels decreased to below the wilting point. High accumulation/low intensity rains (causing saturation/excess runoff) flooded both upstream and downstream Jessour from 50 mm of cumulative rainfall, whereas high intensity/low accumulation rains (causing infiltration/excess runoff) activated the downstream Jesr from an intensity of 15.2 mm/h, and a combination of moderate intensity and moderate accumulation rains activated both Jessour from an intensity of 8 mm/h and a cumulative rainfall of 33 mm. We propose to set 50 mm of cumulative rainfall and/or 6.4 mm/h of intensity as threshold values for the activation of the Jessour system in Zmerten. However, significant soil moisture recharges can occur even without activation of the Jessour system.

During the last two decades, the interest in the heritage values of geodiversity, mainly related to geology and geomorphology, has increased (Reynard and Brilha, 2018). Among the different methods used to analyse the geodiversity, geomorphological mapping can be considered as one of the main tools for the inventorying, assessment and valorisation of geoheritage sites.In this study, we compared two legend systems to analyse the contribution of each to the representation and mapping of various geomorphological landscapes. The two legend systems considered are the UNIL (University of Lausanne) legend and the CGMED-Tunisia (Laboratoire de Cartographie Géomorphologique des Milieux, des Environnements et des Dynamiques) legend. Both were used to map four sectors: (i) the Sebkhet Oum Ez-Zessar Ramsar site on the Gulf of Gabes coastline and (ii) the Wadi K'hil watershed on the Dahar Plateau, both located in south-eastern Tunisia, (iii) the Ferpècle glacier forefield and (iv) the Sanetsch area, both located on either side of the Upper Rhone valley in the Western Swiss Alps.In addition, the combination of the contributions of these two legends has made it possible to elaborate a geotouristic legend (Ghram Messedi et al., 2021) and, from this, to produce four geotouristic maps. These maps emphasise the geoheritage and geotouristic interests of Sebkhet Oum Ez-Zessar and Wadi K'hil, which fall within the perimeter of the UNESCO Dahar geopark project in Southeast Tunisia, as well as the importance of the Ferpècle glacier forefield geosite, part of which is listed in the federal inventory of alluvial areas of national importance illustrating rapid climate change, and the Sanetsch glacier-karst area listed in the inventory of Swiss geosites.Key-words: Geomorphological mapping, Geotourism maps, Tunisia, Switzerland.ReferencesGhram Messedi A., Ben Fraj T., Ben Ouezdou H., Clivaz M., Comisso C., Lambiel CH., & Reynard E., 2021: De la carte géomorphologique à la carte géotouristique : Proposition et application d’une méthode de représentation cartographique par SIG. Géomorphologie : relief, processus, environnement, vol. 27, n° 1, p. 69-87, DOI:10.4000/geomorphologie.15394Reynard E. & Brilha J., (ed) 2018: Geoheritage: assessment, protection and management. Elsevier, Amsterdam, 450 p.

L'étude s'intéresse aux cas de Sabria et d'Aouinet Rajeh. Ces villages sont des exemples types de sites fortement exposés au risque d'ensablement. Ils se caractérisent par un écosystème fragile, par des conditions climatiques contraignantes et par une exploitation irrationnelle du milieu. Une approche diachronique et comparative a été adoptée. Elle vise à la cartographie de l'évolution des formes d'accumulation éolienne entre 1990 et 2022 et à l'étude de la dynamique d'ensablement. Les observations montrent qu'Aouinet Rajeh se trouve dans un état très avancé de dégradation, jusqu'à atteindre un stade d'irréversibilité. Cela a provoqué son abandon total et il n'en subsiste que des témoins sous la forme de ruines. À Sabria, l'ensablement prend de plus en plus d'ampleur, faisant peser une menace majeure sur l'oasis et les différents aménagements.