Built

by Roma Agrawal

  But even though our planet is called ‘the Blue Planet’ because of the amount of water it contains, the shimmering, salty swathes of sea that cover most of the Earth’s surface are not potable. We humans need easily accessible fresh water if we are to survive. But here’s the problem: we don’t actually have much of this. If all the water on our planet was represented as an area the size of a soccer pitch, then the freshwater lakes on the planet’s surface would be the equivalent of the cushion I have on my sofa, while the surface rivers would fit inside the coaster I use under my tea.

  Finding water is hard enough – and that’s why many of our ancient towns were founded on the banks of a river – but as they grew into cities, as fields growing crops became vast, and as we migrated to live further and further from water sources, moving water became a challenge. It’s no wonder, then, that in ancient times humans developed extremely inventive ways to track down and transport fresh water. Even today, engineers work hard to create solutions for this technically challenging process, and in parts of the world it is still a huge hurdle to be surmounted.

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  Like many others of the times, the ancients in Persia struggled to find fresh water. In the centre of Iran there is a large, dry, arid plateau that only receives a tiny amount of rain – less than 300mm – each year. As you fly over the country, desert stretches out below you, bleached of colour by the relentless glare of the sun. Occasionally, though, near small villages and towns, or even in seemingly uninhabited patches of the desert itself, you’ll notice ‘holes’ in the sand. From a vantage point high in the sky, they look like the little crab holes that pepper the beach in Mumbai where I grew up. (I used to sit and stare at them for ages, waiting and hoping for a scuttling creature to appear.) But these holes are neatly arranged in straight lines, and are in fact much larger. Thankfully, they weren’t the work of some giant crab, but were dug by humans, over the past 2,700 years. And throughout that time they have been essential to the survival of the people that live there.

  These holes are part of the kariz, as it’s known in Persian (or qanat, in Arabic): the system used by the ancient people of Persia to bring their life force – water – from below the ground.

  To see how they were built, let’s transport ourselves to the desert of two and a half millennia ago. The muqanni or worker looks near a hillside or slope for signs of the presence of water – a fan of deposited soils, perhaps, or a change in the type of vegetation. At a promising location, he takes a spade and digs a cylindrical well just over half a metre in diameter. To move the dirt he uses a windlass to haul a leather bucket full of soil up and down. Under the blazing sun, he keeps at it, hoping to find damp soil – a possible sign that the water table is close. Sometimes, he goes down as far as his tools will let him, but he doesn’t find anything. At other times, he finds water hiding very deep, more than 200m down. Once in a while, he need only dig down 20m before he finds moisture. That’s on a good day.

  An ingenious kariz.

  But the muqanni’s work has only just started: it’s still possible that all he has found is a tiny bit of water that will quickly run out. He needs to make sure that his discovery is the real thing. So he leaves his bucket in the new shaft and, over the next few days, checks how much water, if any, has collected in it each morning. If he wakes up every day to a full bucket, he knows he has struck gold – or, rather, something even more valuable: he has found the face of the aquifer (an underground layer of permeable rock that contains water). He and his fellow muqanni then dig wells, one after the other, in a straight line down the slope of the hill.

  Using a plumb line to measure depth, the muqanni dig each of these wells slightly deeper than the previous one. It may seem strange to dig a line of wells like this, but here is where the ingenuity of the muqanni lies: their village contains 20,000 people, and trekking up the hillside, drawing water and carrying it back would be a laborious task. Of course, this is done in many places around the world, but here the terrain – the hilliness and type of soil – means the muqanni can make the villagers’ lives easier.

  The wells finished, the workers start to dig a tunnel horizontally from the base of one well to the base of the next, creating a conduit about 1m wide and 1.5m high – just big enough for them to walk through so they can build the next phase.

  This tunnel slopes gently, joining up the bottoms of the wells, and will bring the water out of the mountain. The slope of the tunnel is important: if it is too steep, the stream of water will be too strong and fast, eroding the soil and eventually causing it to collapse. If, on the other hand, the slope is too gradual, water will not flow easily, and will stagnate.

  The muqanni light an oil lamp and place it at the mouth of the tunnel. And as they march into the mountain, they watch the flame so they can make sure they’re working in a straight line. Noxious fumes may emerge from the ground to suffocate them, so the oil lamp not only acts as a beacon but as a kind of warning light: if the flame burns steady and bright, there’s enough oxygen around. If it burns a different colour or goes out, it shows there are other gases present. There are other hazards too. Loose or crumbly soil could cause the tunnel to collapse, so where required the muqanni make hoops of baked clay and push them into the tunnel. The hoops act like two arches joined together: the weight of the loose soil pushes on to the hoops and puts them into compression. Clay is strong in compression, so the hoops reinforce the tunnel and stop it caving in.

  There is a final hazard to be broached when the workers reach the head well (the first well, with its base at the face of the aquifer). They have to break through the aquifer very carefully, otherwise a jet of water might burst through and drown them. Managing all this safely depends on the muqanni’s experience being passed from generation to generation: the techniques used to build kariz today haven’t changed a great deal since ancient times.

  The length of the conduits varies hugely, from 1km to over 40km. Some produce continuous water while others are seasonal. To maintain the system, the muqanni use the extra wells they dug. The frequent build-ups of silt and debris can be removed using the windlass to lower buckets into the wells. With regular repairs they can last a very long time.

  There are said to be over 35,000 kariz in Iran – networks of hundreds of thousands of underground conduits all built by manual labour and still providing an important source of water. The city of Gonabad houses the oldest and largest known example in the country. It is 2,700 years old and its 45km conduit provides water for 40,000 people. The main well is deeper than The Shard is tall.

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  Digging down to an aquifer was one strategy the ancients had for supplying their citizens with water. But with water sources, terrain and tools differing across civilisations and eras, other ingenious solutions were invented, including many we still use today. By the end of the eighth century BC, the two canals providing water for Assyria’s capital city, Nineveh, were no longer adequate to serve the burgeoning population. King Sennacherib (who reigned between 705–681 BC) – had previously used his engineering skills to dig canals through Babylon to flood and destroy it. Now, he was forced to find an additional source of water and channel it to Nineveh. He started nearly 50km away, at the watershed of the River Atrush. From here he constructed a canal to the headwaters of the River Tebitu to increase the amount of water the Tebitu received. The river had earlier been dammed to create the reservoir that had supplied most of Nineveh’s water. This extra water would flow to his city through the two existing canals, increasing its supply.

  There was, however, one problem. To get from the river to the canals that led to Nineveh, Sennacherib’s new conduit had to cross a small valley and, without a water pump, there was no way to push water up the far slope. Undeterred, Sennacherib conceived a structure that could carry water across the valley – what we know as an aqueduct. We think of the Romans as the foremost engineers of aqueducts, but the Assyrian king’s edifice predates their efforts by several hundred years, making it one of the
oldest such structures in the world. You can still see its remains at Jerwan in northern Iraq.

  Technically, the word ‘aqueduct’ refers to any artificial channel used to transport water from one place to another: it can be a canal, a bridge, a tunnel, a siphon (a pressurised pipe), or any combination of these systems. The Nineveh aqueduct bridge was the greatest construction of Sennacherib, a master builder who also created much of Nineveh’s civic architecture, including the legendary ‘Palace Without a Rival’; he may even have been responsible for the Hanging Gardens of Babylon. Over two million cubes of stone went into the aqueduct’s construction, each about half a metre wide. The end result was 27m long and 15m wide, made from pointed corbelled arches (a curved shape supported by projecting pieces of stone) that were over 9m high. A channel on top of the bridge allowed water to travel across the valley. The channel was lined with a layer of concrete to prevent the water from leaking away.

  A corbelled arch.

  Incredibly, the new canal and aqueduct bridge were completed in only 16 months in 690 BC. When the structure was nearly complete, Sennacherib sent two priests to the upper end of the canal to perform religious rites. Before the allocated time for the ceremony, however, the gate holding back the water suddenly opened, releasing the river into the channel. The engineers and priests were terrified of the reaction this might provoke from the king, as Nature had defied his wishes. But the king decided this was actually a good omen, because the gods themselves were so impatient to see his great work completed that they had caused the gates to fail. He went to the head of the canal to inspect the damage, had it repaired, and rewarded his engineers and workmen with brightly coloured cloths, golden rings and daggers.

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  Finding and transporting water are two of the engineer’s big challenges. But once you’ve got it, you have to know what to do with it: the third, equally important challenge, is storing it, ready for use. The Romans, who took aqueduct engineering to an impressively sophisticated level, came up with suitably ambitious storage solutions, such as the Basilica Cistern, situated in – or, rather, under – the centre of Istanbul in Turkey.

  Basilica Cistern, Istanbul.

  The Romans didn’t invent the cistern: since at least the fourth millennium BC people in the Levant region (modern-day Syria, Jordan, Israel and Lebanon) had been building structures to hold water. Cisterns might seem like simple things to make, but in truth the biggest ones are impressive feats of engineering. The Basilica Cistern, for example, has immense walls – up to 4m thick – to resist the pressure from multiple gallons of stored water. To stop water leaking out, the Romans carefully sealed the walls with a coating of lime plaster about 10mm to 20mm thick. Since the roof of the cistern supported a public square, it had to be strong enough to support the weight of buildings, roads and pedestrians above.

  When I visited Istanbul, the sun had pushed the thermometer to a stifling 35° Celsius, and I was grateful to descend the old stone steps into the cool air of the cistern’s vast underground space. Uplighters emitted an orange-red glow and soothing music played in the background from speakers I couldn’t see. I stepped onto raised wooden planks built recently to allow tourists to walk around. Below me, there was a pool of crystal-clear water a few inches deep in which grey, ghostly carp silently swam. I stood watching them, until I was jolted out of my daze by drops of water falling on my head and arms.

  I looked up to see a roof made from beautiful red Roman bricks – the flat kind – with thick layers of mortar between them. Large arches spanned between numerous columns to create a grillage. Between these arches stood quadripartite vaults (domes which are divided into quadrants by four ribs). The breathtaking structure was held up by 12 rows of 28 columns, 9m high, all made from marble and arranged in a regular grid pattern. The tops of the columns varied – some had classical Greek and Roman designs on them; others were plain and bare – they had been salvaged from temples or other ruined structures. Some of the columns had split over time and were strapped together with flat pieces of black iron. A couple had the head of the Greek Gorgon Medusa carved at their base, the venomous snakes of her hair curled menacingly around her face. Her gaze was said to turn people instantly to stone, but here one of the carved heads lay upside-down while the other was on its side – a haphazard arrangement that somehow negated the deadly effect of her gaze. One column, known as the peacock column, was engraved with a curious pattern of circles and lines: these represent the tearful eyes of hens, and apparently the column was built as a homage to the hundreds of slaves that died during the cistern’s construction.

  A quadripartite arch.

  The Basilica Cistern was built by Emperor Justinian in AD 532. Lying beneath the Stoa Basilica, the large public square on the first hill of what was then called Constantinople (after the Emperor Constantine, who in AD 324 made the city the capital of the Roman Empire), it was capable of holding 32 Olympic-sized swimming pools’ worth of water. The cistern received its water via an aqueduct that was connected to natural springs near the region of Marmara. It serviced the Great Palace, the residence of the Roman emperors, until they moved away, and it was subsequently forgotten about. In 1545, a scholar called Petrus Gyllius was talking to local residents as part of his research into Byzantine antiquities. After a little persuasion and coaxing, he discovered they had a mysterious secret – they could lower buckets through holes in their basement floors and miraculously haul up fresh, clean water. Sometimes, they even found fish swimming in their buckets. They had no idea why or how this happened – they were just glad to have a source of clear water (and sometimes even food), and until Gyllius came along, they had kept the secret to themselves. Gyllius realised that their homes must be above one of the famed Roman cisterns, investigated further, and found it.

  I for one am glad he did – the place has a dramatic magic of its own, and has captured the imaginations of many people, including the thousands of tourists who have visited since it was refurbished and reopened in 1987. And, of course, the director of From Russia with Love, who filmed James Bond and Kerim Bey punting stealthily among the columns in sharp grey suits, on their way to spy on the Russian embassy.

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  It’s incredible that something as big and impressive as the Basilica Cistern could simply be forgotten. It’s incredible, too, how cavalier the Romans appeared in their attitude to water. Many historians believe that the rainwater they received was enough to live on, and that the aqueducts were for their baths and fountains. It seems extraordinary to perform such ambitious feats of engineering just for luxury and indulgence, particularly because in many parts of the world, then as now, water was in short supply and it took every ounce of an engineer’s ingenuity to make it count.

  In 2015 I visited Singapore to stay with a friend in her flat on the fourteenth floor of a tower block with wonderful views over the city. I checked with her that the tap water was safe to drink (of course it was) and that she had hot water available for a shower after my long flight. She warned me not to waste water, to turn off the shower when I was soaping myself and to make sure no water was dripping when I had finished.

  I was impressed at her efforts to preserve water and be eco-friendly, but a longer conversation we had after my shower made me realise why this was. From a young age, it had been drilled into her by her parents, her school and her college that water is a precious resource not to be wasted. This is because Singapore has no natural aquifers or lakes. There are a few rivers that have been dammed to create reservoirs, but the country basically has no natural sources of water. Throughout its history, whether under British rule or as an independent nation, supplying its inhabitants with enough water has been a constant challenge.

  The earliest sources of water in Singapore were streams and wells, which served the country adequately when the population was a mere 1,000. But after 1819, when Sir Stamford Raffles made the country part of the British Empire, the numbers greatly increased. By the 1860s, 80,000 people were on the island, and t
he rulers began building reservoirs to store water. In 1927, an agreement was reached with neighbouring country Malaysia, enabling the Singaporeans to rent land in Johor, from where they could pipe untreated water from the Johor River. In a reciprocal arrangement, another pipe from Singapore to Johor enabled the islanders to return some water once it had been treated. During the invasion and capture of the island by the Japanese in the Battle of Singapore (in 1942), the pipes were destroyed, leaving the people with enough water for just two weeks. ‘While there’s water, we fight on,’ declared the region’s commanding officer, Lieutenant-General Arthur Percival – but on 16 February he was forced to surrender.

  This dire situation stayed in the minds of the people long after the Japanese left – to be replaced once more by the British – until 1963, when the country became, briefly, part of the Malaysian federation. So when Singapore gained full independence on 9 August 1965, water self-sufficiency was one of the government’s top priorities.

  In 1961 and 1962, Malaysia signed agreements to supply water to Singapore, one of which expired in 2011; the other is set to expire in 2061. For Singaporeans, it’s a vulnerable position to be in, particularly in our water-dependent, high-consumption modern world, and I imagine they are concerned about their autonomy, given that they depend heavily on a neighbour for such a fundamental resource. If, for example, the whole area were to experience a drought, Singapore might end up at the mercy of another country. So for Singapore, water is as fundamental to its national interests as medicine or spies are to others.