The Stream, March 15, 2023: Another Round of Flooding Expected in California as Atmospheric Rivers Persist

The Manzanita park and ride, located beneath Highway 101 in California’s Marin County, floods frequently during high tides. Brett Walton/Circle of Blue


  • After a weekend of intense rain and flooding, another atmospheric river is expected to sweep across California
  • A new study shows the potential for constructed wetlands, which are already used in over 50 countries, to improve wastewater quality and mitigate greenhouse gas emissions.
  • In Colombia’s Magdalena River basin, which is overrun with Pablo Escobar’s hippopotamuses, biodiversity and water quality is at risk.
  • After nearly two centuries of resource extraction that ignored treaty rights and generated billions of dollars in Canada, courts will soon rule on how much money the British Crown will owe 21 First Nations tribes.

Water defenders in Mexico’s Chihuahua state stage silent protests with weekly cleanups of the heavily dammed and irrigated San Pedro River. 

“There’s not a single institution that dedicates itself to registering species here, little less defending them. What we know about the river’s biodiversity we know because a small part of society takes its time to go and see.” — Enrique, co-founder of Vida en el Río San Pedro (names changed to protect identities). 

The San Pedro River, which loops for over 130 miles in northwestern Mexico, is an integral part of one of the country’s most important river networks. The river also supports a number of Indigenous tribes and is a beacon of life in a dry landscape. 

But between dams, diversions, illegal dumping, and drought, the San Pedro’s health has suffered for the past century. Litter lines the riverbed in many places, threatening species of local and migratory birds, and in some bends the river hardly exists at all, dried-up and shallow. Agriculture is the overwhelming industry in many areas around the San Pedro, and diverts the water. 

A growing number of people are speaking for the river, which is ignored by the authorities, Sapiens reports. Those who do speak, do so in acts of “silent protest.” Vida en el Río San Pedro, a nonprofit which works in the Centro-Sur region, meets weekly to pick up trash from the San Pedro’s riparian zone. Though a physically small act in the face of the river’s many challenges, it is a community effort of resistance and solidarity in the grand stage of environmentalism in Mexico — one of the deadliest countries for such activism.

— Christian Thorsberg, Interim Stream Editor

Recent WaterNews from Circle of Blue

The Lead

California is again bracing for heavy rains and anticipated flooding, as yet another atmospheric river — a large, windblown corridor of moist air originating from the tropical Pacific — is set to make landfall in the state. 

Last week’s storms, which prompted a state of emergency in 21 counties, dropped over a foot of rain in central California, and over 10 inches in the state’s northern regions, NPR reports. The downpours triggered mudslides, flooding, and at least one levee breach in the central coast town of Pajaro that displaced about 1,700 people. 

At the storm’s peak, 37,000 households were without power, and 9,000 people were ordered to evacuate their homes. According to NPR, at least two deaths have been confirmed. 

As the second atmospheric river arrives, high elevations in the Sierra Nevada may receive up to another foot of snow, the New York Times reports, and waterways with already-high water levels, such as the Salinas River, are likely to further rise.

This Week’s Top Water Stories, Told In Numbers


Percent of organic matter removed from wastewater by hybrid constructed wetlands, a new Nature study finds. Constructed wetlands are man-made habitats that use soil, microorganisms, animals, and different species of plants to improve water quality. Currently they are used in over 50 countries. Hybrid versions of the natural facility combine two or more types of constructed wetlands: including different water flows, plants, or soils. This setup, researchers at Shandong University in China found, can also remove 63 percent of nitrogen and 72 percent of phosphorus from wastewater, and release the fewest amount of nitrous oxide, methane, and carbon dioxide emissions.



Number of hippopotamuses that today live in Colombia’s Cocorná river, 30 years after Pablo Escobar’s original four “pets” escaped from his property. The population’s boom in the decades since has created an ecological dilemma in the Magdalena River basin, the Guardian reports. Not only do local river communities and fishermen live with anxiety as confrontations occur more frequently, but the mammals are also eating massive amounts of fish, putting endemic endangered species — including the West Indian manatee, neotropical otter and spectacled caiman — at further risk. Moreover, hippopotamus poop is toxifying the river, killing additional fish. By 2034, the hippo population is expected to surpass 1,400.

On the Radar

Twenty-one First Nations tribes are seeking billions of dollars from the Canadian government after 173 years of unpaid annuities, “in a case that could set legal precedents across the country by formally recognizing Indigenous interpretations of historic treaties,” The Narwhal reports

In exchange for the ability to grant mining patents on Anishinabek land, the government signed the Robinson-Huron and Robinson-Superior treaties in 1850, which promised annual payments to the tribes along Lake Huron that would increase “if resource extraction revenues grew.” More than 77 total mines, profiting a total of $330 billion, have since been built and operated on the lake’s shore, in addition to the presence of lumber and fishing businesses. But according to The Narwhal, annual payments were raised only once, in 1875, from $1.70 to $4 per person. 

Joseph Stiglitz, the former Nobel-prize winning economist hired by the tribes, estimates that they are owed over $100 billion. Private negotiations are ongoing, though the decision could set a precedent for future payments, especially those relevant to shorelines and water systems.

More Water News

US Drinking Water: The EPA has announced its first-ever proposed standards for toxic “forever chemicals” in drinking water. According to CNN: “The proposal would regulate two chemicals, PFOA and PFOS, at 4 parts per trillion (ppt). For PFNA, PFHxS, PFBS and GenX chemicals, the EPA proposes not one standard for each but a limit for a mix of them.”

New Zealand: Twenty-three scientists from around the world concluded that global warming worsened the flooding caused by tropical cyclone Gabrielle in New Zealand last month, AP reports.

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