One pipe, one river: what Calgary and Maringá got wrong about water

The City of Calgary has told us to expect about four more weeks of Stage 4 water restrictions this fall. Not because of drought. Crews are tying a new 6 km feeder main into the system, and the old pipe has to come out of service to do it. That makes three times in 28 months that a single pipe has decided how much water 1.6 million people can use. I lived and studied civil engineering in Maringá, in northern Paraná. In January 2016, Maringá lost most of its water too. Not to a pipe, but to a river. I started this post wanting to argue that Calgary should have built something more distributed, like home. The numbers didn't let me. Maringá, January 2016: the river came to the pumps Maringá takes about 91.5% of its distributed water from one source: an intake on the Pirapó River. The rest comes from a handful of wells. After days of heavy rain, the Pirapó rose and flooded the intake. Five pump motors were damaged, including 1,500 hp units that had to be craned out and sent to Londrina for repair. Sanepar, the state utility, pulled crews in from Cascavel, Foz do Iguaçu, Ponta Grossa and Curitiba. The city went on rodízio , rotating supply by neighbourhood. When two motors came back from the shop still faulty, restoration slipped again. The neighbourhoods fed by wells barely noticed. Afterwards, Sanepar spent more than R$27 million hardening the intake, including electrical centres raised above flood level so the pumps keep running when the river comes up. The state also announced more wells and a study of the Ivaí River as a second source. Calgary, 2024–2026: one pipe, 60% of the water The Bearspaw South Feeder Main carries about 60% of the treated water for Calgary, nearby municipalities and the Tsuut'ina Nation. It broke in June 2024 and again in December 2025. Each break meant weeks to months of restrictions. The inspection numbers are the part that stuck with me: 239 of roughly 2,000 four-metre pipe segments were deteriorated, about 12% of the line, with 23 needing urgent repair. Calgary's response is now a parallel 6 km replacement, due to be commissioned in December, plus a 22 km North Calgary feeder main under construction and a 25 km South Calgary main in planning. Both cities route most of their water through one asset. Shares are approximate. Maringá was more centralized, not less This is where my argument fell apart. I expected the Brazilian city to look more resilient on paper. It's the opposite: one river intake carrying 91.5% of supply is a bigger concentration of risk than one pipe carrying 60%. So the lesson isn't that one country builds better than the other. Both cities bet their water on a single artery. What differed was what happened after it failed. The difference is repair time A flooded pump at a river intake is a visible, accessible failure. You wait for the water to drop, crane the motor out, rebuild it, put it back. A utility can stock spare motors. That's days to a couple of weeks, even when the repair shop sends one back broken. A buried 1,500 mm steel main under a residential street is a different job. Locate the break, excavate, dewater, cut out segments, source new steel, weld, pressure-test, disinfect, refill. Nobody keeps a spare kilometre of large-diameter pipe on a shelf. That's weeks to months. In software we'd call this the difference between how often something fails and how long it takes to recover. A database with a single primary is a single point of failure either way. But a primary you can fail over in five minutes is survivable. One that takes three weeks to restore is an outage that makes the news. Both cities also had partial redundancy, and it mattered. Maringá's wells kept some neighbourhoods normal. Calgary's Glenmore plant is why the city got restrictions instead of dry taps. Neither had a full second path for the main supply. The rule I'd apply to any city, rich or not: no single asset should carry more than about half the supply unless it can be bypassed (and the bypass has actually been tested) or repaired in days. Put differently: for every critical asset, multiply its share of supply by its realistic repair time. The biggest product is your real risk, and it's a list that fits in a spreadsheet. Both cities are now moving that way: Maringá by hardening and adding sources, Calgary by building parallel and new mains. It just took a failure each to get there. What you can do in the next four weeks Rainwater won't replace a feeder main, but it can carry your garden through a restriction. The maths is simple: 1 mm of rain on 1 m² of roof is 1 litre. After gutter and first-flush losses, expect to keep roughly 80–90%. So a 100 m² roof in a 10 mm rain gives you about 800–900 litres. A typical 200 L rain barrel fills with just 2.5 mm of rain on that roof. For most houses the barrel, not the roof, is the bottleneck. Before you use it, check what the current restriction stage allows. If you want to size a proper cistern, my rainwater calculator uses the Rippl method from Brazilian standard NBR 15527. Today it covers Brazilian cities, including Maringá. Canadian cities are next on the list, and this post is the reason why. Where this breaks This is a back-of-envelope comparison, not a forensic report. The supply shares are approximate and change with demand and season. The two systems serve very different populations (about 430,000 vs 1.6 million). I don't have a confirmed end date for Maringá's 2016 rotating supply, so I haven't claimed one. And "repair in days" assumes spares and crews are available, which Maringá's delayed motors show isn't guaranteed. Sources ABRH: Maringá water supply system, Pirapó share AEN Paraná: Sanepar intake flooded by the Pirapó (2016) Banda B: damaged motors and rotating supply (Jan 2016) AEN Paraná: raised electrical centres, R$27M+ invested City of Calgary: Bearspaw South Feeder Main update Global News: feeder main supplies 60% of treated water CTV News: deteriorated segments and new feeder main projects