In a photograph made in 2025, a water measurer in Ben Aissa holds a copper plate above the channel. He plugs openings with clay until the water steadies, then records what each family is due. The plate is not a universal gauge: its openings stand for locally defined shares. At Timimoun, one opening on the top row represents a tmen, a unit of about 0.0416 litres a second.[1][2] That small adjustment links an underground gallery to a garden, a family and a community’s account of its water.
The system is the foggara, the Algerian member of a much wider family of gently sloping underground galleries known elsewhere as qanats.[6] In the Touat and Gourara oases of Algeria, south of the Tadmaït plateau, galleries collect groundwater and carry it toward cultivated land by gravity.[3] A 2016 technical paper describes more than 1,400 foggaras and over 2,000 kilometres of galleries across the broad Tadmaït, Touat and Gourara area. Those are the authors’ regional inventory figures, not a present-day count; surveys made in other years and with different boundaries report different totals.[3] The clever part is visible above ground only at the end: a comb of stone, a copper plate, and the patient work of dividing water fairly.
Timimoun sits amid an inhabited chain of oasis settlements in the Gourara. The town’s architecture and palm gardens belong to a landscape shaped by scarce surface water and the old routes that connected the ksour.[4] The foggara is part of that settlement pattern: it makes cultivation possible where a permanent river does not run through the oasis. Its route also ties distant points together, from the mother well to a communal channel and the separate plots at its end.[3]
Where the Water Comes From
The galleries tap the Continental Intercalaire, the deeper of two aquifer layers in the North-Western Sahara Aquifer System.[3][7] The system extends across Algeria, Tunisia and Libya. Its water accumulated over long periods, though the Sahara and Sahel Observatory’s model describes some recharge, concentrated near the Atlas, Dahar and Djebel Nefoussa ranges.[7] This is a useful distinction: old groundwater can be replenished slowly, but that does not make every local supply secure.
A foggara collects water only where its gallery runs below the water table. The water table is therefore the quiet limit on its yield; a pump can draw from deeper ground and keep going after a gravity-fed channel weakens.[3] In the whole transboundary aquifer system, estimated withdrawals rose from roughly 0.6 billion cubic metres a year in 1970 to 2.5 billion in 2000, compared with a modelled recharge of about one billion.[7] The Observatory identifies the western basin, including Gourara, Touat and Tidikelt, as an area with meaningful recharge potential, while also documenting declining foggara flows.[7]
A gallery has a collecting reach and a carrying reach. The upstream portion lies in saturated ground and admits water; the downstream channel brings it toward the oasis, losing some along the way. In an estimate attributed to Algeria’s national water agency in 1983, those conveyance losses were 10 to 20 percent.[3] When the water table recedes, the point where it meets the gallery floor shifts back toward the mother well, and the discharge falls.[3] A person standing at the stone comb sees the result, though the change began far underground.
The geometry matters. A gallery has to descend gently enough for water to move, while staying close enough to the water table to intercept it.[3][6] A steep route would run too quickly and a shallow one might fail to reach the saturated ground. The shafts help define that route during construction and later cleaning, but from the surface they resemble a dotted line across the desert. Their mounds are the visible trace of a long passage hidden below.[3]
Digging the Gallery
Excavation proceeded from the place where water would be used back toward its source, according to a general account of qanat construction.[6] In Touat and Gourara, the drier first stretch was easier; the saturated upstream section brought mud, unstable walls and the risk of collapse.[3] The same technical paper admits that the method used to dig the wettest section remains poorly explained. That uncertainty is a reminder that an old technology can be well described in its finished form while the knowledge of its builders is harder to recover.
Vertical shafts gave workers access along the route, lifted spoil and let air circulate; they did not collect the water themselves.[3] Their lines can be picked out from above by the mounds of rubble left around each opening.[3] A 1998 inventory by the national water agency reported shaft spacing of five to 23 metres in the surveyed galleries.[3] In the qanat photograph below, the tunnel is a narrow hand-cut passage; an Algerian foggara follows the same broad principle, though its route and dimensions respond to local ground.[6]
Scale varied from one oasis to another. The 2016 paper describes El Kebira at Ksar Metarfa, in the Aougrout oases, as a 14-kilometre gallery; it reports El Meghier, the largest in Timimoun, at nine kilometres.[3] These examples make the labour tangible: a route measured in kilometres had to remain open, graded and connected to the level of groundwater. When declining flow called for a longer collecting reach, some communities extended the gallery upstream in a practice called tarha.[3] In a few Timimoun oases, a smaller gallery downstream of the first was also dug to recover water that had seeped away.[3]
The Stone Comb That Splits the Flow
At the outlet, the water enters a basin and meets the kasria, a flat stone comb whose openings divide the flow.[8] A small basin and baffle slow the current before it reaches the slots.[2] Their widths matter: each opening represents a share in the water, and the larger comb may split the flow into several channels before smaller combs divide it again.[1][2] The channels end at family basins called madjen, from which gardens are irrigated.[3]
El Meghier offers a glimpse of the branching scale. The cited study describes one main comb feeding four secondary combs, then 22 tertiary combs and 286 basins.[2] More than 200 families depended on this foggara, and a portion of its flow was assigned to Timimoun’s communal pool.[2] The stone comb in the photograph at Tala is a small, visible end to a network whose social reach extends well beyond the channel itself.
Here the system differs from the khettaras of Morocco’s Tafilalt region. There, the cited comparison describes water allocated to irrigators in turns; a 32-turn cycle could take 16 days to come around.[2] In Timimoun, by contrast, owners receive a continuous trickle at the same time, with the volume set by their shares.[8] A steady allotment helps explain how palms, grain and vegetables can grow together in the same oasis garden.[2]
The shares are tied to contribution: owners’ water rights reflect what they contributed to digging and maintaining the gallery.[3] A council known in the British Museum’s account as the Djmaa (also transliterated djamaa) oversees local management, while the water measurer translates the opening widths into allocations.[1][2] The arrangement turns maintenance into a continuing obligation. A share is not just a claim on water; it connects a household to the work that keeps the source flowing.
That pattern of branches turns one physical flow into many social relationships. The first opening does not decide an owner’s share on its own; the local unit, the contribution behind the claim, and the accepted measurement all matter. The method can therefore vary from oasis to oasis without losing its central logic: a measured portion is assigned, carried to a basin and recorded so that the next measurement has a point of comparison.[2][3]
The Measurer and His Copper Plate
The measurer’s title appears as kayal in the British Museum’s 2025 account (also written kial el ma in a 2014 study). The person is chosen for honesty, reliability and skill, and each oasis has its own measure, unit and measurer.[1][2] UNESCO has described these water measurers as a key figure in the life of the Saharan ksour.[9]
The copper plate carries the local calibration. In Timimoun, the top row of the louh has openings around seven centimetres wide, each counted as one tmen, approximately 0.0416 litres per second.[2] Other openings represent fractions or multiples of that local unit. The reading is therefore not simply a count of holes: it is the count interpreted through the unit and calibration used by that oasis.[2] The study records a different unit in Ouled Said, the habba or habba zrig, based on a smaller opening.[2]
The plate is part of a small working group. An accountant adds the figures; a worker shapes the clay that holds the instrument in position; another official announces each owner’s total.[2] The measurer tests the openings one by one and writes the results on a clay tablet. If an owner repeatedly disputes a figure, a second measurer can be called.[2] There is no machine doing the social work of making a measurement accepted.
The figures pass into a register called the zamam (also spelled zemmam), where changes in flow, cleaning, and transfers of shares are recorded.[2] Researcher Juan Ignacio Robles photographed a register from Ben Aissa, written in Arabic script and kept at the mosque of the ksar of Othmane Ben Aissa. It was brought to a meeting of the Djmaa.[1] Owners also paid the measurer in crops once a year, with contributions tied to the basins served.[2]
That work is becoming harder to pass on. In 2018 UNESCO placed the knowledge and skills of the water measurers of Touat and Tidikelt on its List of Intangible Cultural Heritage in Need of Urgent Safeguarding.[10] The committee’s decision notes that while registers exist, the craft itself was never systematically recorded in writing.[9] The contrast is sharp: the numbers have a book, but the skill that turns water into numbers still depends on people who know the plate.
Gardens Under the Palms
The last channel brings water to a family basin beside the walled garden, the gamoun.[3] Continuous flow through channels and basins helps sustain a cool, damp growing environment beneath the palms, according to fieldwork in Timimoun.[2] A garden can hold several layers of cultivation: date palms above, cereals and vegetables below. The water share sets the rhythm.
Robles and collaborators Tarik Ghodbani, Mohamed Hadeid and SidAhmed Bellal followed farming across two years of fieldwork. Their account traces cereals sown in October, vegetables planted in January, hand-pollination of palms in March, and dates gathered in June and July.[1] The sequence makes the garden’s dependence on an even supply clear: work under the palms changes with the season, but the channel is expected to keep delivering.
Their research describes local seed varieties and a polyculture that supports pollinating insects.[1] The same fieldwork argues that this form of peasant production has helped maintain food security, while warning that the shift toward wells and pumps puts it at risk.[1] Beneath the palms, water management and cultivation are not separate subjects. The shape of a household’s share influences what it can plant and when.
Maintenance preserves more than the channel’s carrying capacity. When the gallery is cleared, the renewed flow is measured and the shares can change accordingly; the register makes that change legible to owners.[2] That gives the summer work an immediate consequence. Clearing a blockage can restore water to a garden, while the new reading gives the community a common record of what has returned.[1][2]
The Summer Cleaning
A foggara gradually silts and can collapse. Small slips of earth narrow the channel; a larger failure in the carrying section can block it and fill the access shafts with water, making repairs harder.[3] A study of Timimoun distinguishes threats by setting: drifting sand and plants trouble some galleries near the erg, while collapse is a greater risk for galleries cut in the Albian formation.[5] Qanat channels elsewhere also need periodic removal of sand and mud.[6]
In Timimoun, communities organise this work as tuiza, also commonly written touiza: a collective maintenance effort carried out in summer.[1] The reported timing makes it possible for young people and children to join, since they can fit into the narrow galleries more easily.[1] After cleaning, the measurer checks the flow again with the louh, and the updated amount is redistributed.[2] The work in the tunnel and the record at the comb belong to the same cycle.
Pumps, Counts and Repairs
That cycle is under pressure. An Adrar water directorate census from 1959–61 recorded 909 active foggaras among 1,416 in its survey area; a later agency survey, conducted in 1998–2001, counted 903 functioning systems.[11][8] A 2015 report citing the agency gave a later Adrar total of 679 active and 758 dried foggaras.[11] These are dated inventories with their own survey boundaries, not figures to combine into a single precise decline rate.
The sources identify pumping and boreholes as major pressures, alongside drought, the movement of people away from rural areas, and the division of shares through inheritance.[8] Local reporting adds road construction, urban growth and deep wells near foggara lines.[11] In 2015, association president Moulay Abdallah Smaili described young people’s declining interest as a serious obstacle to preservation.[11] UNESCO likewise records ageing practitioners and too few successors.[10]
Restoration projects have targeted galleries, and an observatory for foggaras was established in 2011.[11] Yet a repaired tunnel cannot by itself restore the local knowledge that decides how much water each opening carries, who maintains the channel, or how a change is entered in the register.[2] That is why the copper plate remains such a useful image of the whole system: it is a measuring tool, but also a compact record of shared work and mutual claims.
At Ben Aissa, the register returns to the mosque after the meeting. Its pages can preserve each adjustment to the flow, but only a practiced measurer can set the plate in the current, read the local unit and make the allocation understood. The foggara’s future rests in that passage of knowledge, from one hand at the comb to the next.[1][9][10]
.jpg){kind=link}
Share what you know
Been there, grew up there, or know something we missed? Add a comment; corrections with a source are especially welcome.