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.
Entre quatre et cinq terrasses, une série de cônes de déjection coalescents, deux glacis d'érosion et un glacis de substitution constituent la gamme des formes quaternaires dans la Jeffara septentrionale et la partie nord-orientale du plateau du Dahar-Matmata. Compte tenu des données géomorphologiques, préhistoriques et chronologiques, tous les dépôts datent du Pléistocène supérieur et de l'Holocène, exceptés la croûte calcaire attribuée au Pléistocène inférieur qui scelle le premier glacis d'érosion, et le dépôt conglomératique à poudingue pouvant appartenir à la fois au Pléistocène moyen et supérieur. Les croûtes calcaires, les changements de faciès et l'agencement des formes témoignent du rôle déterminant des changements climatiques dans l'évolution géomorphologique quaternaire de ce domaine aujourd'hui aride.
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