The rivers located in large cities that relieve a planet full of polluted water

The mesmerizing scene on the banks of the lime-green Isar River in Munich on a recent summer afternoon made me, an outsider, tremble with envy. Groups of students, after-hours employees, families, and nude bathers were sprawled on blankets with bottled beer and light meals. From time to time a bather or someone on a floating tube passed by in the swift current.

In 2000, before the climate crisis accelerated, turning summers into hellholes marked by record high temperatures, the city of Munich undertook a radical restoration of the Isar, which flows north from the Alps, crosses the center and empties into the Danube. The 11-year, $38 million effort involved purifying the Isar’s waters, extending its floodplains and modifying its banks to accommodate torrential spring snowmelt.

The restoration was intended to benefit flood-prone neighborhoods as well as the river’s flora and fauna. But today the river is also an easily accessible public space that offers essential relief from the heat. “I don’t have a balcony, I don’t have a garden, but I have the Isarsaid a friend who lives in an apartment and swims there regularly.

Urban residents everywhere deserve the same opportunity. If cities invest in cleaning up their waterways, they will create crucial lifelines to make the hottest months more bearable in environments disproportionately hit hard by global warming. Paved surfaces absorb heat, and buildings and narrow streets trap it, putting urban populations at greater risk than rural ones. Healthy rivers are just the kind of “green infrastructure” that cities need—ecosystems that significantly improve the quality of urban life.

Many urban rivers are not safe to swim in because they have been polluted by countless forms of pollution. One of the culprits is the toxic runoff of everything from pesticides to trash that flows from rooftops, parking lots, yards, and city streets during heavy rains.

In many places, upstream farms and factories also spew fertilizer, chemical and animal waste, adding to the toxic concoction. E. coli bacteria and other pathogens can spill from sewer systems and treatment plants overwhelmed by downpours. But the experience of Munich and a handful of other cities in Europe and the United States shows that it is possible to curb all these forms of pollution, build better sewage and treatment systems, and contain stormwater runoff so that it is safe enough for swimming. .

Munich and the State of Bavaria built 19 purification stations along the river along the Isar and its tributaries. The plants treat the wastewater and during the most popular swimming months employ ultraviolet light disinfection systems to reduce the bacteria count in the water. The high concrete-lined embankments of the river were also demolished and replaced with expanses of grass and pebbles where floodwaters could rise and fall unimpeded.

In addition to making humans feel fresher and happier, the restored ecosystem has been a boon to the Collared Flycatcher and other birds, and Danube salmon, a species that lays eggs at the bottom of gravel beds. of the streams. The Isar transformation has been so successful that city planners from Singapore to Seoul have visited to learn from it, according to Munich officials.

A few other countries in Europe now offer similar refreshing options for dips downtown: In Switzerland, swimmers and wildlife have returned to the rivers that run through Basel, Bern, Zurich, and Geneva since the country spent around $56 billion. dollars in new sewer systems, wastewater treatment plants and other facilities. The city of Vienna also offers swimming in the clear and clean waters of the Danube River. And Paris is in the midst of a major effort to halt pollution of the Seine in time for the 2024 Summer Olympics by capturing excess sewage and rainwater in a large reservoir during storms.

In the United States, many urban rivers are so polluted that swimming in them is illegal. But efforts to clean them up are underway in New York, Boston, Philadelphia, Chicago and other cities.

These cities are beacons for others to follow: the investment is huge, but so is the reward.

As climate change increasingly pushes city dwellers into rivers, it is depleting them too. Last year’s drought-plagued summer contracted many of Europe’s great waterways — the Rhine, Danube, Loire and Po, among others — to record levels.

The more rivers recede, the more saline they become and the more inhospitable they are to life. At worst, they become susceptible to toxic algae blooms.

Healthy and resilient rivers are a first line of defense against the impact that rising temperatures will have on all of our lives.

PAUL HOCKENOS
INTELLIGENCE
The New York Times