Benefits of Water-Harvesting Systems (Jessour) on Soil Water Retention in Southeast Tunisia

Abstract

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.

The role of the jessour system for agrobiodiversity preservation in Southern Tunisia

“…The study area includes the villages of Douiret, both the old one and the new one. According to the Institut National de la Statistique the new village host approximatively 600 inhabitants, while the old one-carved in a mountain side-has been abandoned since the mid-1980 during a process of modernization, promoted by the authorities, aimed to renew the country (Bessioud and Mazouz 2017).…”

“…In addition, jessour contribute to wind erosion control, by preventing sediment from reaching the downstream plains, where the wind is very active (Abdelli et al 2017); they are also effective in increasing soil moisture storage, prolonging the growing season for natural vegetation, and decreasing the amount of supplemental irrigation required for growing fruit trees (Al-Seekh and Mohammad 2009). The Jessour are traditional water harvesting techniques widely used for growing crops and fruit trees, allowing the cultivation of olive, almond and fig trees beyond their climatic zone (Calianno et al 2020).…”

Upstream-Downstream Influence of Water Harvesting Techniques (Jessour) on Soil Water Retention in Southeast Tunisia

“…The Jessour form a hydraulic unit made of three main components: (i) a dam (locally called Tabia or Ketra) between 2 and 5 m high and between 15 and 50 m long across the talweg [2], in the form of a small earth embankment, sometimes reinforced with stones, with a lateral spillway (called a Menfes) or a central spillway (called a Masraf) made of stones; (ii) a terrace which includes the cropping area (called Khliss); and (iii) an impluvium, which is the runoff sub-catchment area [2,11,35,36]. The Jessour take advantage of The Matmata-Dahar plateau lies in the upper arid bioclimatic region [31] and is located in the transition zone between the Sahara to the southwest with a subtropical, dry and hot climate, and central Tunisia to the north, which is influenced by a relatively temperate Mediterranean climate [5].…”

“…The Jessour form a hydraulic unit made of three main components: (i) a dam (locally called Tabia or Ketra) between 2 and 5 m high and between 15 and 50 m long across the talweg [2], in the form of a small earth embankment, sometimes reinforced with stones, with a lateral spillway (called a Menfes) or a central spillway (called a Masraf ) made of stones; (ii) a terrace which includes the cropping area (called Khliss); and (iii) an impluvium, which is the runoff sub-catchment area [2,11,35,36]. The Jessour take advantage of short rainfall events occurring in autumn and winter by collecting and slowing down runoff generated at the level of the impluviums [11]. In the wet season, when the soil is well supplied with water, the upper horizons provide water to fruit trees (olives, almonds, figs) and potential intercropping (lentils, peas, oats).…”

“…The present paper focuses on the soil moisture dynamics of Jessour and is the continuation of the work of Calianno et al [11] that compared the ability of a Jesr to store soil moisture in comparison with a similar site without a Jesr in the Dahar plateau (region of Zammour). On the one hand, previous works have already shown the quantified added value of water harvesting techniques on soil moisture using water balance or rainfall-infiltration modeling [12][13][14][15] and remote sensing [16].…”