Two cities, continents apart, are both challenged with water quality — and how to govern it alongside farmers. In Toledo, Ohio, Lake Erie faces warmer temperatures, nutrient runoff from tributaries and harmful algal blooms. In its sister city, Toledo, Spain, the Tagus River suffers from downstream pollution from Madrid, low water flows and an uninhabitable river for citizens.
The relationship was formed in 1931 through Sister Cities International, the first partnership of its kind. Over the years, the cities have shared architectural influences, art exchanges and regional economies that are both driven by agribusiness. But a crisis in one city has accelerated research and solutions in many others.
Northwest Ohio’s 2014 water crisis jumpstarted measurable change in Lake Erie’s health. Harmful algal blooms threaten drinking water supply, caused by urban and agricultural runoff of phosphorus, in addition to poorly regulated industrial polluters.
Beatriz Larraz Iribas is a research faculty member at the University of Castilla-La Mancha in Toledo, Spain and directs the Tagus River researcher group called Tajo UCLM-SOLISS. Compared to Lake Erie, their approach to protecting waterways is proactive.
“I don’t need fire in the river. I don’t need more dead fish to begin to solve the problem. It’s enough,” she said.
In Spain, a lack of water flow in the Tagus River is caused by diverting nearly half of its supply to an agricultural region in the south. Then, waste water dumping caused a bathing ban in the early 1970s and ecological wipeouts. Citizens lost access to their river.
Requiring water to irrigate and fertilizer to grow, farmers found a seat at the negotiation table offering economic counterbalances in a rush for environmental solutions. But both cities stand, still knowing long-term solutions to struggling water systems and ecosystem health have not been found.
Safe drinking water at the cost of the environment
The majority of drinking water in central Spain comes from the Sierra de Guadarrama Mountains, deposited into reservoirs called Entrepeñas and Buendía. Safe and accessible, the water supply supports the seven million residents of Madrid, who are closest to the reservoirs and cities like Toledo directly south.
But the management of wastewater reflects the same downstream consequences seen around the world. Madrid’s six wastewater treatment plants lack modern infrastructure, resulting in the discharge of polluted water into the Jarama River, a major tributary of the Tagus. Flowing north to south, the Jarama meets the Tagus, which runs east to west through Toledo before emptying into the Atlantic along Portugal’s coast.
Consistent cases of dead fish and year-round foam are attributed to ammonium levels 50 times higher than the permitted limit. Nitrates exceed their maximum permitted level 56 percent of the time, and phosphate concentrations reach 25 times higher than allowed, the research team said.
Left: Beatriz Larraz Iribas points to sites on the Tagus River where ecological transition is being tracked. Right: Foam develops on the shore of the river in Toledo, Spain. (TFP photo by Jake Zajkowski)
Although Canal Isabel II, Madrid’s public water company, has national mandates not to pollute, Larraz says, “They prefer not to invest in treatment plants and continue like that [pay endless penalties], and the governments permit it.” The Tagus River Basin Authority is in charge of such accountability.
Citizens were the first to notice the water dwindling, becoming more polluted. Warning signs were posted along the river that limited its use.
“It wasn’t activists, but it was people from the village,” Larraz said.
Safont Beach, an access point below the city of Toledo, Spain where Toledo Free Press interviewed the researchers, was once a regular bathing area. As water flow declined from Madrid to Toledo, authorities announced in 1972 that bathing in the river was prohibited due to health concerns. It wasn’t until 2009 that the Plataforma de Talavera de la Reina en Defensa del Tajo was formed, a civic group advocating against degradation and for increased river flow.
Later in 2012, researchers and watchdogs organized a research team led by Larraz to study the history, law, biology and chemistry of the Tagus River. Formed to create solutions and accountability for the deteriorating water system, the research team has grown to 40 members, following a 2021 partnership with the Soliss Foundation — a regional insurance company.
Their work now studies emergent pollutants in the Tagus River. One project Beatriz explained involves “comparing with the rest of the rivers in the world that have recovered the water quality.”
While researchers from the two Toledos haven’t worked together before, they are familiar with U.S. water issues, citing river fires in Cleveland — one of the origins of the Clean Water Act — in addition to algal blooms in Toledo, Ohio.
For both cities, an early indicator of safe waterways was swimmability. What they share, like rivers across the world, are historical scenes of recreation rarely seen today. Regular swimming without concern occurred on the Maumee River and at the mouth of Lake Erie until about 1985, when the International Joint Commission designated it an Area of Concern due to contamination.
Agriculture and clean water trade-offs
The underlying cause of poor water quality in the Tagus River is the lack of flow. Hydroelectric dams slow the river’s natural east-to-west movement, and tributaries are diverted through a project more than a century in the making: the Tagus–Segura Water Transfer.
Producing one-quarter of Europe’s produce, southern Spain hosts one of the most concentrated, yet efficient, farming systems in the world. The region of Murcia supports outdoor, irrigated horticultural crops. In Almería, just east, low-tunnel greenhouses produce vegetables across 20 miles of plastic-covered land.
The Spanish state planned this water transfer in 1933, recognizing the region’s Mediterranean temperatures and sunlight perfect for produce growing. Construction finished in 1979, and the system — capable of transferring 158.5 billion gallons of water per year — became operational in 1991.
“This type of agriculture drinks whatever they want — no limits. They, without this water, couldn’t survive,” said Larraz. Water from the Entrepeñas and Buendía reservoirs is split, with nearly half sent to Murcia and Almería, and the rest flowing into tributaries and the Tagus River.
Exploitation rules limit how much water can be transferred. “In the national water plan it is said that the Tagus River has the priority to use the water before the water is transferred. But that law is not being followed. The farmers have a lot of power, because they are the ones that export to Europe,” she said.
Beatriz’s team consistently reexamines solutions outlined in international policy papers but says economic trade-offs continually obstruct problem-solving. Europe is generally self-sufficient in produce, dairy and wheat. Prioritizing a reliable food supply for Europe has overshadowed environmental policy and equity for cities like Toledo, Spain.
Parallel to U.S. policy, the Clean Water Act regulates point-source pollution, but nonpoint-source exemptions mean nutrient runoff, manure and pesticide applications fall outside federal authority — leaving local governments to develop solutions.
Regulating the watershed
What one city avoids, the other confronts. In northwest Ohio, state-led governance has helped curb runoff into the Maumee River and Lake Erie since Toledo’s 2014 drinking water crisis.
Under protocols set by the International Joint Commission between Ohio, Michigan and Canada, phosphorus reduction targets were established, though they are not always met.
Jordan Hoewischer, director of water quality and research for the Ohio Farm Bureau, said in a statement, “OFBF, along with the rest of the agricultural community, has gone above and beyond to help solve the water quality challenges of our state and has committed millions of dollars to water quality and nutrient management research, as well as providing strong support of Governor DeWine’s H2Ohio program, and those efforts at the farm level are making a difference downstream.”
Over the past 30 years, farmers have reduced fertilizer use by 33 percent, and 65 percent of Ohio counties have recorded phosphorus declines through soil testing, according to OFBF. Acknowledging agriculture’s role in runoff alongside climate factors such as rainfall and warming lake temperatures, Ohio launched H2Ohio, investing $270 million in wetlands and conservation practices.
H2Ohio has 2.5 million acres enrolled across Ohio, supporting conservation agriculture in grain crops. (TFP Photo by Jake Zajkowski)
Participation in land management reforms remains voluntary in both Ohio and the European Union — an approach often criticized for uneven results. After seven years of H2Ohio subsidies, lawmakers continue to debate whether improvements in Lake Erie can be directly attributed to wetlands or on-farm practices. While environmental obligations persist, the urgency that followed the 2014 crisis has faded, and a long-term water bill has stalled repeatedly.
Globally, agriculture exerts outsized political influence — not due to population size, but because of its role in gross domestic product and food security.
In Spain, progress has been slower. Larraz said outreach to policymakers has fallen flat. “We speak with the politicians here in Castilla, Almanza and with the water authority in Spain or in the towers river, but they don’t listen.”
Under the EU Water Framework Directive, rivers must reach good ecological status by 2027. “This directive has a date, a final day to be in good status. And we are not going to obtain that,” said Raúl Urquiaga Cela, a researcher at Tajo Chair UCLM-SOLISS.
Environmental groups have succeeded in securing a minimum flow requirement for the Tagus River — previously the only major Iberian river without one. The decision sparked protests from farmers who argue drought conditions could threaten their livelihoods. AP News reported Lucas Jiménez, president of the Central Irrigation Union, telling a crowd, “Let them leave the water in the hands of those who understand water.” Spain’s minister of ecological transition warned the 2023 protests not to escalate into a “water war.”
Science alone has not shaped the policies around water, as Toledo, Spain advocates and scientists explain. But the political will, enforcement and governments’ willingness to confront the agricultural and economic forces will define watersheds.
