A Continuum of Time and Space: Community Design of Runoff Water-harvesting Systems in Chenini, Tataouine

Introduction

Change, an intrinsic aspect of our world, operates in diverse and complex rhythms, constantly challenging our understanding. This unfolding phenomenon transcends the boundaries of time and space, urging us to contemplate our connection with the natural environment.

The redefinition of this relationship should be in a ‘retrospective foresight’ manner that cumulatively and collectively accommodates the social, cultural, and economic context of each community. While more challenging in practice than in theory, Southern Tunisia provides an intriguing case study through its integrated and participatory water management practices.

Water management has consistently held a fundamental role in sustaining both urban and rural settlements, with its significance magnified in drylands. Despite the inherent water scarcity, inhabitants of such areas collectively observed, evaluated, and developed systems of coping with such a challenge [1]. These long-established systems not only reflect a profound understanding of the local environment but also exemplify mature and tacit ‘’landscaping thought’’ [2], re-conciliating man’s needs and that of nature leading them to coexist, albeit not always harmoniously. This relationship with nature is to be understood as an evolving and dynamic dialogue rather than a fixed endpoint. One that remains susceptible to a myriad of natural and anthropogenic induced disturbances, as will be elaborated in this article. Understanding this relationship as a continuum allows us to leverage past and existing knowledge and use it as a stock for ‘’grafting’’ when dealing with new challenges to the system.

The ‘continuum effect’ is visually evident in the extensive historical utilisation of water-harvesting systems that span the entirety of the Tunisian territory, encompassing approximately one million hectares [3]. Systems that are particularly prevalent in the arid expanse of Southern Tunisia [4] (Figure 1). Within this rich mosaic, Tataouine, positioned as the southernmost and largest Tunisian governorate, stands as a veritable repository of Jessour (singular: Jesr) and Tawabi (singular: Tabia) systems. These intricate systems cover around 400,000 hectares [5] of the rugged Matmata mountain range, which traverses the southern governorates from northwest to southeast with a varying altitude of 600 meters in the north to flat topped plateaus rising to heights of 400 meters in the southern reaches [6].

Jessour systems occupy intermittent mountain gullies and thalwegs to accumulate runoff water and sediment [1,7-13].They are composed of a 2-5m high trapezoidal earth dykes (AR: Tabia), of 1-4m in width, usually reinforced with local stone, with side or central spillways (Menfes and Masraf respectively) [4,10,15,13,17]. As sediment accumulates behind the Tabia, it gradually shapes a terrace, which serves as a cultivation area and the receptor of runoff water from the impluvium or sub-catchment area [12,13,17]. The proportion of Tabia reinforced with stone is contingent upon factors such as the terrain's slope, the runoff water flow's intensity, and the quantity of soil resources on site [18]. Chahbani (1990) states that it could be totally constructed from stone in small and steep narrow valleys where the earth is prioritised as an agriculture medium rather than a construction material.  

The water-harvesting system effectively utilises the limited annual rainfall in the region, averaging between 150-200mm, characterised by its high intensity and low frequency, and most commonly occurring during the winter season [17]. This efficiency is achieved by slowing down runoff water, resulting in soil moisture levels equivalent to an annual rainfall of 500 mm, nearly 2.5 times the actual amount [8]. The enhanced moisture, combined with sediment build-up, creates favourable conditions for various agriculture, including the cultivation of olive, almond, fig, and palm trees, as well as legumes, wheat, barley, and numerous native herbaceous plants [7,13,14].

Limiting our discussion to the physical description of the Jessour system, as presented above, would confine it to the status of an isolated object, a critique often directed at contemporary architecture both locally and globally. Instead, the following will provide context to the system and its relational dimension in the mountain village of Chenini and its newer urban counterpart ‘’Nouvelle Chenini’’, southwest of Tataouine [19], particularly by examining the role of the community within this system and its inter-connectedness with the built environment across different temporal perspectives – the past, the present, and the future (Figure 2).

Customary Rules, Collectivism and Landscaping Thought

The establishment of the Berber community on the Chenini ridge dates to the Roman times, initially on the northern and northeastern sides and subsequently the more fortified southwestern and southeastern slopes of the mountain [19,20]. The village gradually grew in three tiers, following the natural topography of the ridge. These tiers are connected by a meandering sloping path designed for both pedestrian and donkey traffic, with steps added for pedestrians where ground levels permit [20]. From a climatic perspective, it is evident that, the selection of this location was not only rational due to its proximity to seasonal wadis but also because of the climatic advantages of the altitude [20]. The elevated position provides relatively milder thermal conditions, mitigating the effect of both diurnal and seasonal temperature fluctuations [17,20]. Interestingly, this was complemented by the thermal mass effect of Chenini’s subtractive architectural housing typology known as 'Gheyran' (singular 'Ghar') [19-20]. These lateral cave dwellings were collaboratively carved into the mountains, through a process of communal construction, and the excavated rock was repurposed to construct the protruding rooms that surrounded them (Figure 3) [20]. Considering the agro-pastoral activities of the residents, the settlement also included common service buildings dedicated to the processing and preservation of agricultural products, including the oil mill (Ar: Ma’sara) and the collective granary (Ar: Kell’a or Kasr) [19-20].

Regarding collective planning and management, the Jessour system was no different, where it strongly relied on the social cohesion of the community and its tribal structure.

Distinctively and intentionally in Chenini, water rights were separated from land tenure and ownership for while the land was privately owned (Ar: Melk) and managed by the extended family, water rights were governed by a tailored set of internal customary rules [20,23]. These rules stipulated that no owner possessed the authority to obstruct upstream spillways, and any modifications to upstream- Jessour required the consent of the downstream owner [22]. In a similar vein, the management of wells (Ar: Bir), adhered to the Waqf system where regardless of ownership, all settlement inhabitants and their livestock were entitled to utilise the water resource [20,22,23].

The sustainability of the system was not merely an intellectual endeavour, relying solely on upstream and downstream dependencies, and the strategic placement and sizing of spillways. It also necessitated ongoing maintenance efforts. This entailed ploughing the land pre-rainy season, to assure infiltration, but also tasks such as: addressing breaches caused by erosion or rodent activity, gradually raising the tabias due to sediment deposition, and maintaining the weirs and spillways [3,8,24].

While the maintenance efforts aligned with the sedentary farming lifestyle of the Berbers residents, it is important to note that Chenni's territory was not an enclosed one. Its dynamism can be attributed to the presence of their cohabitants, the Arabs, who practised inter-territorial transhumance and together engaged in trans-Saharan caravan trade with Ghadames, Libya [20]. This mobility, combined with the implicit comprehension of the local environment, bestowed upon Chenini the capacity for adaptability and resilience in the face of harsh conditions, particularly during times of diminished rainfall and crop yields.

The Descent, Hurdles and Re-invention

Change being a certainty, the Tunisian landscape has encountered various challenges necessitating novel solutions. One such encounter arose during the period of French rule from 1881 to 1956 when efforts were made to centralise land and water management. This move was driven by the pursuit of modernisation, the desire for territorial control and abolishing collective management [5,22]. Subsequently, in the 1970s and 1980s, the administration focus shifted towards implementing large-scale hydraulic structures, including dams, as a means to achieve greater stability and productivity in response to the growing population and food demand [3,17].

Simultaneously, rural migration patterns led to the abandonment and deterioration of many small-scale hydraulic systems, a situation exacerbated by extreme flooding events in 1969, 1979, and 1990 [3,5,15,16,18].

Chenini experienced the adverse effects of the factors mentioned above. on the village level, it descended from the mountain to the foothills [19,21]. This transformation was aided by the introduction of new building materials, primarily bricks and reinforced concrete, as well as the subsequent installation of overhead electricity and a potable water supply systems [20]. These developments gave rise to Chenini’s eastern counterpart ‘’Nouvelle Chenini’’ (Ar: Chenini al Jadida), with its ‘new’ urban pattern, housing styles and associated public buildings including primary schools, post offices, hotel, and accompanying retail establishments [25]. The winds of change also extended to the cave houses. Zindi (2018), provided a detailed account of the transformations that occurred within the Ghey’ran where some of these structures were left vacant, while others underwent modifications and expansions using materials sourced beyond the locality.

The Jessour system experienced a relatively better transformation compared to Nouvelle Chenini. During the 1990s, there was a shift in the treatment of small-scale hydraulic systems, which began to be regarded on equal footing with larger ones within an integrated water management approach implemented by the administration [3].

This approach aimed to acknowledge and capitalise on traditional knowledge, as well as the expertise of academics, while considering the unique characteristics of Tunisia's various climatic zones [17].

In this context, the Jessour system was valued not only for its capacity to support rainfed agriculture but also for its vital role in groundwater preservation, aquifer recharge and as a measure for flood control and combating wind erosion, thereby safeguarding downstream infrastructure and settlements [15,17,18]. Furthermore, it was appreciated for providing a distinctive habitat, within a harsh environment, for local flora and fauna [7,26]. This manifested itself physically in the reinvented typologies of the system (Figure 4) as follows:

- Jessour system built following the traditional way with the earthen dyke and the natural stone reinforcement, using manual labour or a hybrid of manual labour and loader trucks (Figure 5).

- Mechanical Tabia: Typically executed by Regional Commission for Agricultural Development or awarded to local contractors, these structures serve the purpose of check dams for flood control and are typically left uncultivated [28]. This Tabia construction involves the use of natural stone gabion baskets to create a stepped cascade for the Menfes, and the shoulders on both sides [17,27]. The primary design objective here is to minimize the need for short-term maintenance. However, Bonvallot (1986) criticises this approach for its lack of flexibility compared to earth weirs, which can naturally widen due to lateral erosion of the slope.

- Finally, A Jessour’s replica for piedmonts: constructed in an L of C-plan shape, usually situated in gentle sloping plains which, taking advantage of the plain’s milder topography, are longer, have larger terraces and are relatively not as high as their upstream counterpart (1-1.5 m) [7,17]. Farmers opt for constructing these Tawabi despite the high hourly cost of loader trucks [28]. They prefer them due to their larger cultivation area and the associated profits [3,28]. Governmental grants and initiatives from local NGO’s are incentivise for this typology with a best practice community-based project implemented over 600 hectares in Hariza-Chaab Chenini Region in 2015 [28].

The previous typologies work in harmony, with the Mechanical Tabias serving as a safeguard against severe flooding in the piedmonts and by so reducing maintenance works. Furthermore, when combined with the larger hydraulic structures, create the regional water management trail.

Scarcity, Uncertainty and Room for Improvement

Despite the bleak outlook of future climate conditions, the continued over-exploitation of deep-water resources, and ongoing migration trends, which all contribute to heightened uncertainty and scarcity (both natural and constructed), these circumstances are familiar in southern Tunisia. It is imperative to remain to perceive them as constraints rather than barriers [29] which necessitates further contemplation, refinement, and optimisation of the status quo. There is a need for substantial improvements in funding mechanisms. While governmental grants are available for the construction of Tabias, streamlining bureaucracy and extending loans to cover maintenance is essential [27,28]. Moreover, the process should focus on strengthening its horizontal collaboration and fostering the active involvement of civil society, research institutions, and individual academics. It should also seek inspiration from successful local practices, such as participatory rangeland management, to promote cross-pollination of ideas and solutions.

The Tunisian experience exemplifies one that did not deal with indigenous and traditional knowledge in a tokenistic or folkloric manner and kept the community in the heart of the process. One that initially capitalised on social cohesion, customs, and networks beyond their local geography [20,23] and as it developed, did not ‘’chuck the baby out with the bathwater’’, but built upon existing policies and the heterogeneity of administrative bodies to reach a similar output.

Conclusion

The article emphasises two key points.

First, it underscores that the ‘thought’ process of the Jessour’s evolution holds significant promise for making substantial contributions to improving the climatic resilience of urban areas in contemporary settlements within the region. Second, it highlights that despite the multitude of rapidly evolving approaches and concepts, such as Sponge Cities, Green Infrastructure (GI), Sustainable Urban Drainage Systems (SuDs), Nature-based Solutions (NbS), and others, which predominantly originate from international knowledge realms, it is vital not to feel overwhelmed to the point of aversion or excessively captivated by these terms. Instead, it stresses the importance of embracing a ‘global’ perspective to progressively uphold the ‘continuum.’