Thirsty Places: Monterrey

The Cerro de la Silla stands over Monterrey like a saddle left on a fence, and in the summer of 2022 the people of the city took to driving out past it on a Sunday to look at a dam. The Cerro Prieto reservoir, an hour to the southeast, had supplied a share of the city's water since the 1980s, and by June it was a plain of cracked grey mud with a trickle in the middle and, where the water had been deepest, the road and the walls of a village drowned forty years earlier standing in the open air. People walked out across it and took photographs. Behind them, in the city, the taps came on at four in the morning and went off at ten.

This article is about where Monterrey's water comes from and why one dry year emptied it, what six hours a day looked like for five million people, why the breweries became the villains of the summer, what the storm that ended it left, and what the city is building so the next one is survivable.

Three dams in dry hills

Monterrey is the industrial capital of Mexico, a city of five million in the northeast that makes the country's steel, glass, cement and beer, five hundred kilometres from the sea, in semi desert hills that get about six hundred millimetres of rain in a wet year and half that in a dry one. It drinks from three dams: La Boca, the small old one in the mountains to the south; Cerro Prieto, built in the 1980s on the San Juan river to the southeast; and El Cuchillo, the largest, built in the 1990s on the same river further downstream and nearer the Rio Grande, from which an aqueduct of more than a hundred kilometres pumps water back up to the city. Between them, with the wells in the city's own ground, they had been enough through the growth of thirty years, in a region whose rain comes in bursts from the tropical storms of late summer and whose dry years come several together.

The dry years came from 2019. The storms missed the Sierra, the rivers that fill the dams fell to nothing, and the city went on using what it used, about four hundred litres a person a day in the wealthy districts of San Pedro and a fraction of that on the hills where the pipes barely reached. By the spring of 2022 Cerro Prieto was below one percent, La Boca was at a tenth, and El Cuchillo, the one reservoir with water, was at under half and falling, with the farms downstream on the Rio Grande holding a prior claim on part of it under an agreement with the neighbouring state. The aqueduct from El Cuchillo could carry only what it could carry. In June the state government did what the places articles on this site have seen done in Cape Town, Chennai and Bogotá: it rationed.

Six hours

The scheme was six hours: pressure in the pipes from four in the morning until ten, then nothing until the next day. The city's households filled whatever they had, tanks on the roof for those with tanks, buckets and bathtubs for those without, and learned the arithmetic of a day on what six hours would fill. It was not six hours everywhere. Monterrey is a city of hills, and the colonias on the slopes, where the poor live, are at the ends of the pipes and the tops of the pressure zones, and when the whole city opened its taps at four the pressure never climbed to them; many got two hours, or an hour, or the tanker. The water utility and the state ran hundreds of tankers to the hills, free, and the queues and the fights around them were the summer's pictures, with the private tanker trade, which the Delhi article on this site describes in its most organised form, charging what the hills could pay. Schools closed early. The hospitals, which the hospitals article explains cannot run without it, were put on a separate supply. The utility moved to a rota of sectors, each with its day, as Bogotá would two years later, and the rota ran through July and August in temperatures above forty degrees.

The breweries

The anger needed a target, and it found the companies. Monterrey is where Mexico's beer comes from, the home of the Cuauhtémoc brewery since 1890 and now of Heineken's largest Mexican plant, and of the bottlers of Coca Cola for the north of the country, and these plants hold concessions for groundwater and river water granted by the federal government decades ago, under a system in which the concession is a right and the city's water board holds a different one. In a normal year the concessions are a few percent of the basin's water and nobody notices them. In June 2022, with the taps off at ten, the sight of a brewery running was intolerable, and the protests went to the gates of the plants, the governor named them in his broadcasts, and the president said in his morning press conference that the companies should move to the south where the water was. Heineken announced that it would hand over a share of its concession to the city for the duration, and the bottlers followed, under the cameras; the volumes were a small part of what the city needed and a large part of the summer's politics. The question the summer left, which the breweries article on this site asked in general, is who holds the right to a basin's water when the basin runs short, and the answer in Mexico is still the concession.

The storm

The crisis ended the way the region's dry years always end, in a few days of rain. In September 2022 the remains of a tropical storm came in off the Gulf and over the Sierra, the rivers that had been dry for three years ran, and the dams filled: La Boca overflowed, Cerro Prieto went from mud to a third in a week, and the rota was lifted. The relief was real and the lesson was the one the Montevideo article on this site drew a year later: a city living from a few reservoirs in a climate of bursts is one dry run of years from the rota, and the rain that saves it does not say when it will come next. The year after, the dams were at normal levels and the city used what it had used before.

What is being built

Two projects came out of the summer, and both had been on paper for years. The first is a second aqueduct from El Cuchillo, finished in 2023, that doubles what the one reservoir with water can send to the city, about five cubic metres a second more, so that the next time Cerro Prieto and La Boca fail the city can lean harder on the one that does not. The second is a fourth dam, called Libertad, on a river to the north that the state began in 2022 and that will add a store on a different catchment from the three that emptied together. There are the other measures the places articles always find: a leakage programme on a network that loses a quarter of its water, meters on the wells, recycled water from the city's treatment plants to the industry that was the summer's villain, and the question, unanswered, of the four hundred litres a day in San Pedro. The city is growing by a hundred thousand people a year on the strength of the factories that the rest of the continent's supply chains have moved there, and every one of them drinks from the same three dams and the fourth.

The factories

The reason the city is growing is the reason the water will be short again. Monterrey is the capital of what the trade press calls nearshoring: the move of factories from Asia to northern Mexico to supply the United States across a border three hours away, and Nuevo León has taken more of it than any state, with industrial parks going up on the dry plain around the city and the announcements of 2023, among them an electric car plant that was to be one of the largest in the world, promising hundreds of thousands of jobs. Each plant drinks. A car assembly plant, which the car article on this site describes, uses a few cubic metres of water per vehicle; a glass works, a steel mill and a brewery use more; and the state's answer, in the permits for the new parks, has been to require recycled water from the city's treatment plants for the industry that can use it, which the Cerro Prieto summer made politically necessary and which the city's three works can supply only in part. The governor who ran the rationing of 2022 announced the car plant in 2023 on the same platform, and the question the two announcements put together is the one the Phoenix article on this site asked of a desert city that is growing on the strength of its industry: how many dry years the fourth dam buys, and who is at the end of the pipe when they come.

What it teaches

Monterrey is the city on this site where a rich industrial region met the rota. The dams were the right dams for the climate until three dry years arrived together, the city's use had grown to the full supply of a normal year, and in the summer when the reservoirs ran down there was nothing to do except open the taps for six hours and send trucks up the hills. The beer and the soft drinks, which were not the cause, carried the blame because they were visible; the fix, an aqueduct and a dam, was the one the city could have built in the wet years and did not. The storm refilled the dams in a week. The factories are still coming.

Six hours a day, a drowned village in the open air, and a brewery handing over its water under the cameras.