The circularity of water: the key for living in the desert

The M’Zab valley in the Algerian Sahara

By Mohamed Amine Saidani [1]

 

In the M’Zab oases in the Algerian Sahara, the local communities progressively developed, from the 11th century onwards, an ingenious circular hydraulic system as the only water in the valley comes from the rare flash floods (0 to 2 floods per year). The hydraulic system was designed to capture the floods and recharge the shallow groundwater aquifer through a diversity of hydraulic devices. The water was then made available to the community, for drinking and for irrigation of crops, through shallow wells. The principle of circularity is not limited to water, but was also applied to i) the agro-ecological association of agriculture and animal husbandry with the reciprocal use of by-products (crop residues; manure); ii) the use of animal traction, including for the lifting of water and iii) waste recycling, which increases the efficiency of resource use, thereby reducing the discharge of waste into the environment.

 

However, the promotion of new Saharan agricultural systems, focused on national food security and economic profitability, over the past 50 years, questioned this circular system. These intensive agricultural systems are generally situated in the so-called ‘extensions’, outside of the existing oases, and rely on pumped groundwater from the deeper, little-renewable, aquifers. The environmental impacts of these extensions – mining of the deep groundwater aquifers, the deterioration of the quality of groundwater and soils – are increasingly criticized. Faced with these environmental vulnerabilities, very localized initiatives are beginning to emerge in order to promote more sustainable forms of agriculture in the Sahara.

 

This research is interested in the analysis of the secular circular system and questions the sustainability of the different forms of irrigated Saharan agriculture in the light of the principle of circularity. In this paper I will look at a concrete case of a farm situated in an extension of the palm grove of Bni Isguen, where the farmer has taken multiple initiatives for more sustainable and more integrated agriculture.


Circularity in a farm located in the new extensions

“On my farm, I collect every drop of water that the good Lord wants to give me, while trying to make the most of it. I apply this same principle at home. I installed water flow reducers on each tap to avoid wastage as much as possible.” It is in these terms that Mohamed* a farmer in the N’tissa irrigation scheme (Bni Isguen) received me. According to him, the harshness of the region in terms of climatic, topographic and geological conditions, coupled with the paucity of flash floods (0 to 2 floods per year), prompted him to collect every drop of water that runs either for immediate irrigation use or to store it in the shallow groundwater table for later use. On his farm, established in 1997, there is an ingenious mix of recharge infrastructure (recharge wells, dikes, basins), inspired by the secular hydraulic system of the M'Zab oases, with more contemporary facilities using new technologies (pumping of flood water, concrete pit to store water in the basement). Initially, Mohamed worked in the plastic industry and did not commit heart and soul to agriculture. He only made a shallow well to provide irrigation water and planted some palm trees and fruit trees. In 2014, at the age of 50, he wanted to change course. He sold his shares in the family-run plastic production company and returned to Ghardaia definitively to devote himself entirely to farming.

Before and after the development of the farm in the new agricultural extension.

The choice of the farm site is not trivial. Mohamed was inspired by his ancestors, when they settled in the region in the 11th century. This is why he chose to settle in a Wadi bed, close to the only renewable water resource. The strategic location of this 3 ha farm, limited by a large wadi (N’Tissa), a small tributary and crossed by a talweg, led him to undertake three types of hydraulic development, inspired by traditional practices. First, the construction of an ahbass (dike) in the talweg, diverting part of the flood water from the small tributary to the farm and recharging the groundwater from water derived from the large wadi. However, Mohamed’s experience in the plastic pipe manufacturing company inspired him to make some changes to the design of this infrastructure. As the farm is located at a higher altitude than the wadi bed, Mohamed has made several material adaptations. First, he designed a 50 m trench under the road to divert and channel the water from the wadi to the farm. Second, he installed a weir in the wadi just after the trench to divert the water to his farm. Third, he designed an underground concrete reservoir to store the derived flood water, which is then pumped to irrigated the land. Fourth, the farm was conceived in terraces separated by low walls (rabetat) to allow the pumped surface water to spread by gravity without causing damage. These walls not only slow down the speed of the water, but also recharge the water table by percolation and retain the sediments of the wadi. Thus, during a flood, the earth being enriched with organic matter, Mohamed does not use the manure produced on his farm.

Hydraulic structure for diverting part of the flood water to the farm.

The agricultural terraces separated by low walls in the farm.

Similar hydraulic infrastructure was designed to divert and channel the flood water from the second wadi. However, the main objective in this case was to recharge the shallow groundwater table with the diverted water. A recharge well was connected to the trench and fitted with a small manual valve to control the incoming water flow. This recharge well, called ouaroura, which in Berber language means to swallow, has actively contributed to recharging the water table and increasing the piezometric level during floods.

The recharge wells inspired by the secular hydraulic system.

 

In addition, the concrete wall of the dike is extended downstream to form a reservoir, which has a double function: irrigation basin for all of the year and swimming pool in summer. The double function of this basin is an ancestral practice in the oases. During the summer, Mohamed welcomes families, friends and childrens’ associations from the region to take advantage of this friendly space and have a good time.

Double function of reservoir, irrigation basin and swimming.

 

Finally, Mohamed is promoting more sober production and consumption modes and was inspired by circular oasis practices, including the recycling of animal and human organic matter, the recycling of waste, nutrients, plant biomass and water. He opened a shop to sell local agricultural products, including olives, olive oil, dates, mint and citrus fruits.

Association of agriculture and animal husbandry with the reciprocal use of by-products.

The circular oasis practices,

including the recycling of animal and human organic matter and the recycling of waste.

 

Despite the advantages that the hydraulic infrastructure provided for the collective interest of the farmers of the N’tissa irrigation scheme, in particular with regard to the recharge of the water table, this irrigation scheme, located upstream of the Bni Isgen oasis, was considered problematic by some. This was the case of the Oumana El Essail, the traditional guardians of the water of the oasis, who wanted to protect the water of their community irrigation system. According to them, the water used in the N’tissa area for irrigation and groundwater recharge, takes away part of the water that for centuries fed the old palm grove of Ben Isgen located further downstream. This shows that the gradual use of secular recharge practices in new agricultural extensions raises new questions at the local level. While on the one hand, more sustainable and environmental-friendly practices on this farm are inspiring other farmers in the region, in particular in the new extensions, there is also, on the other hand increased competition around the surface water resource between the different communities and even between agricultural spaces, ancient oases and new extensions.

* Fictitious first name

 

Reference

de Boer, I. J., & van Ittersum, M. K. (2018). Circularity in agricultural production. Animal production systems and Plant production systems. Wageningen University and Research.

[1] CREAD, Algeria. Agronomy and Veterinary Sciences Institute, IAV Hassan II, Rabat, Morocco. SupAgro, Montpellier, France.

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