The Mother Well

From the air, the approach to Yazd looks like the surface of somewhere that has been shelled. Lines of small craters run for tens of kilometres across the gravel, dead straight or in long curves, each ring a spoil heap around a shaft. They are the ventilation and excavation wells of qanats, and each line marks a tunnel running underground towards the city at a gradient of a metre or two per kilometre — shallower than the slope of the land above it, which is the entire trick. Follow one back far enough and you reach the mother well, the madar chah, sunk into the water-bearing gravels at the foot of a mountain. Follow it forward and you reach a garden, a cistern, a bathhouse, a city.

Iran has tens of thousands of these. Counts differ sharply between sources and the number still flowing is disputed, but nobody argues about the shape of the trend: it has been falling for sixty years, and it is not falling because Iranians stopped wanting water. It is falling because a different way of taking water arrived, because two laws changed who owned it, and because the new method can reach places the old one cannot. The tunnels are drying from below.

What a qanat is, physically

A qanat is not a well and not a canal. It is a gently sloping tunnel, hand-dug, that intercepts the water table under an alluvial fan and lets the water walk out of the hillside on its own. The digger — the muqanni, a hereditary and dangerous trade — sinks the mother well first to find water, then drives the tunnel from the settlement end back towards it, sinking a vertical shaft every twenty to fifty metres to lift out spoil and let air in. Those shafts are the craters. The oldest and largest known example, Qasabeh Gonabad in Khorasan, has a mother well over 300 metres deep and a tunnel running more than 30 kilometres; UNESCO puts its age at around two and a half thousand years, and inscribed it in 2016 with ten others as The Persian Qanat. The technique spread outward under a dozen names — falaj in Oman, khettara in Morocco, karez across Central Asia and into Xinjiang — and it is the reason there are cities in places with no river at all.

Water you could inherit

The part that is easiest to miss is that qanat water was property, and that it was owned separately from the land it irrigated. A share in a qanat was a share of time. The flow ran in a fixed rotation of some number of days, and the rotation was divided into hours and fractions of hours, timed before clocks with a bowl that had a hole in it and sank at a known rate. Those shares were bought, sold, mortgaged, inherited, given in dowry and endowed as religious trusts, and a man could own water in a village where he owned no soil. The mirab, the water master, ran the rotation, kept the register and was paid out of it, and the shareholders funded the maintenance in proportion to what they drew — which mattered, because a qanat that is not cleaned collapses within a few years. The system also had a limit built into its physics rather than into its rules. A qanat drains by gravity from a tunnel mouth at a fixed level: in a wet run of years it yields more, in a dry one less, and if the water table falls below the tunnel it yields nothing at all, no matter how much anyone wants it to. There is no throttle. You cannot pump a qanat harder, and the people arguing over shares were arguing over the division of a quantity that none of them could increase.

A qanat cannot take more water than the aquifer gives it. That was never a conservation policy — it was a fact about gravity, and the pump abolished it.

The laws that took the water

Two pieces of legislation moved the whole thing into the hands of the state. The land reform launched in 1962 broke up the large estates, and with them the landlords who had owned many of the bigger qanats and paid for their upkeep; the smallholders who inherited the plots did not inherit the capacity to maintain a thirty-kilometre tunnel. Then the Water Nationalisation Law of 1968 declared the country's water — rivers, springs, groundwater — national property, held by the state and allocated by permit. The 1982 Law of Equitable Distribution of Water, passed after the revolution, replaced it and kept the same principle: water belongs to the public, the Ministry of Energy licenses its extraction, and historic rights survive only in so far as the ministry recognises them. In one sense this was a modernising reform of the ordinary kind, and other countries have made it. What it did here was dissolve the register — the mirab, the rotation, the shareholders who paid for the cleaning — and put nothing local in its place.

The pump

Motorised deep wells arrived in the 1950s and spread quickly, and they beat the qanat on every measure a farmer cares about. A well takes days to drill rather than years to dig. It goes where you want it rather than where the geology allows a tunnel. It delivers on demand rather than on a rotation. And it reaches below the level a qanat can reach — which is the fatal detail, because a well drilled near a qanat lowers the water table and dries the tunnel without ever touching it. The qanat's owners lose their water to someone who has not taken it from them in any sense a court finds easy to describe. The state has been trying to close the tap for decades: the Ministry of Energy classifies the great majority of the country's aquifer plains as prohibited, closed to new licensed wells, and periodically announces campaigns against unlicensed drilling, which tells you both that the rule exists and that it is not obeyed. Iranian officials have put the number of unauthorised wells in the hundreds of thousands. Those figures are contested and have been revised repeatedly, and the honest summary is that nobody knows the total, the ministry included.

What the ground does about it

Aquifers under the plateau are not caves. They are layered gravels, sands and clays, and the water in the clay is holding the grains apart. Take it out and the clay compacts, the ground above sinks, and the pore space that stored the water closes for good — which is what makes groundwater different from a reservoir, because a reservoir can be refilled. Radar measurements over the Tehran, Varamin, Isfahan and Rafsanjan plains have recorded subsidence at rates among the highest reported anywhere in the world, opening fissures across farmland, cracking irrigation canals and in places undermining railway lines and buildings; the specific figures vary by study and by year and should be treated with care, though the direction does not vary. The clearest place to stand and look at the result is the Khaju bridge in Isfahan, built around 1650 with gates in its piers so that it could hold the Zayandeh Rud back and raise the water for the gardens upstream. For much of the year now there is nothing to hold. The river has been over-allocated for decades — to the city, to steel and industry, to towns downstream, to farmland in the east of the province — and topped up since 1953 by tunnels driven through the Zagros from the Karun basin, which move somebody else's water into this one. In November 2021 farmers from the eastern districts pitched tents in the dry bed in the middle of the city and held it for over a fortnight, until security forces burned the encampment out and cleared the riverbed; mobile internet across the province went down for days around it, and reports of injuries from the dispersal were never independently settled. People sit under the arches in the evening, on sand.

None of this makes the qanat a solution to be restored wholesale, and Iranian hydrologists do not generally argue that it is: the tunnels are labour-intensive, they irrigate what is near them and nothing else, and a country of ninety million does not feed itself on gravity. What the old system had was an accounting that could not be cheated. The flow was visible, the shares were registered, the maintenance was paid by the people who drank, and the ceiling was set by the rock. What replaced it is a permit system administered from a ministry, over a resource that is now invisible, extracted by machines the state cannot count, from a store that does not come back once it has been squeezed flat. The tunnels under Yazd are still worth going down into. They are also the last piece of Iranian water infrastructure that told the truth about how much there was.