Calling two of Europe's most famous rivers "sewers" was a cliche by the 1950s.
The Seine, which flows beneath the bridges of Paris, was declared biologically dead in the 1960s, a cesspit of human, industrial and agricultural waste devoid of all but the most hardy fish.
Across the border in Germany, "Father Rhine", the mighty river that runs for more than 1300km from the snow-capped peaks of the Swiss Alps to the North Sea through Switzerland, Germany, Luxembourg, France and the Netherlands, fared little better.
As early as 1931, the last sturgeon - a long-lived fish sought-after for its caviar - was fished from the Rhine but it was the loss of the river's prized salmon that was mourned.
By the 1950s, the extraordinary journey of the Atlantic salmon, from its European spawning grounds across thousands of kilometres of ocean to Greenland and back again to the exact same stretch of river, was no more.
It was also increasingly difficult to draw drinkable water from the Rhine, particularly for the Dutch, who blamed upstream neighbours for polluting it.
The Rhine is one of the world's busiest waterways; more than 35,000 ships travel some part of its length every day.
The lower Rhine is famous for the historic castles and postcard-perfect villages that cluster along its banks.
Germany's famous Rhineland wine region depends on the river, its vineyards clinging to the impossibly steep slopes of the gorge between Koblenz and Mainz.
By the late 1940s, the Dutch were calling for inter-country collaboration to stop using the river as a waste dump but progress was hampered by the fact that after World War II, no one was speaking to Germany, through which 80 per cent of the Rhine flows.
But as the political situation became more stable, Switzerland, the Netherlands and Luxembourg, with Germany, signed up to a formal plan of action and set up the International Commission for the Protection of the Rhine (ICPR) in 1950.
In the first five years of the commission, sewage treatment plants expanded rapidly and bans were imposed on ship oil waste being dumped in the river, but water quality had barely improved by the 1970s.
Then came the Sandoz fire. In 1986 at Basel, a riverside town in Switzerland downstream from the headwaters of the Rhine, the Sandoz chemical factory, one of the biggest in Switzerland, caught fire.
As firemen battled the blaze, tonnes of polluted water spilled into the Rhine, contaminated with dyes, pesticides and mercury. Townspeople were told to stay indoors, downstream the river ran red.
Within 10 days the toxic soup travelled the length of the Rhine and spilled into the North Sea, killing millions of fish and eels and making the Netherlands water supply undrinkable.
Dr Anne Schulte-Wulwer-Leidig, biologist and deputy secretary of ICPR, says the accident coincided with Europe's growing environmental movement and there was a public outcry.
"After the fire there was a huge protest movement to clean up the river and industries were finally prepared to do it because they wanted a better image in their communities," she says.
Pressure was put on the ICPR to impose stricter regulations on polluters and to make sure a similar disaster could not happen again.
By 1987, the commission had drawn up yet another plan of action but this time it had to convince the populace it meant business.
The plan, with its catchy title of "Salmon 2000", promised the return of wild salmon to the river by the turn of the century instead of relying wholly on artificial stocking of the river and its tributaries with thousands of juveniles.
Over the following decade, nitrogen, arsenic, mercury and lead were cut by between 30 and 70 per cent while dioxins and PCBs were undetectable in water samples by 1992.
By the late 1990s, most of the river's 63 native species had returned after dropping to a low of 29, although the elusive sturgeon remains absent from its former habitats.
By 1994, the work appeared to be paying off as researchers found recently-hatched salmon in the Sieg, a mountain river and tributary of the Rhine that rises in the Rothaar Mountains and flows for 153 km before joining the Rhine near Bonn.
It was the first evidence in decades of natural salmon reproduction in the entire Rhine system.
"In the last 10 years you have been able to fish in the Rhine but the goal is that it will be possible to swim, to have better fish populations that are sustainable," Dr Schulte-Wulwer-Leidig said.
"At the moment it is not sustainable. Salmon populations will need to be managed for 10 to 15 more years."
A major barrier for migrating fish are the hundreds of hydro dams and numerous weirs at regular intervals along the Rhine.
Millions of Euros have been spent on building fish "passages" which allow fish to bypass hydro works but more will be needed if salmon are to swim the 800km from the North Sea as far as Basel, a key goal of the ICPR action plan.
Whether the Seine's salmon will ever return anywhere near Paris remains a moot point although some excitement was generated in late 2004 when a 1.8kg fish was caught 10km upstream - 130km downstream from the city.
The 77km-long Seine is France's second-longest river after the Loire and flows northwest from Burgundy through Paris to the English Channel.
Its banks are a United Nations world heritage site and define the geography of Paris with its Rive Gauche (Left Bank) and Rive Droit (Right Bank).
The river reached its pollution low-point somewhere around the middle of last century when a popular joke ran that a leap off a bridge into the river would not kill you nearly as quickly as a swim in its toxic waters.
"Forty years ago the Seine was biologically dead," says Olivier Bommelaer of the Seine Normandy Water Agency.
The agency is one of six in France, created in the mid-1960s to get local communities involved in managing their own water supply. The thinking was that the more the public were involved, the easier it would be to persuade them to comply with new pollution regulations.
Administered by France's Ministries of Environment and Finance, each agency has its own "Basin Committee" made up of local farmers, residents and industrial users.
The committees get to decide how the billions of Euros from water rates and France's "polluter pays" system get spent each year.
As with the Rhine, the first five years saw a rapid expansion in wastewater treatment, with plants increasing three-fold in the Seine Normandy basin.
Over the next 30 years, industrial discharges to the river and its tributaries were cut by 95 per cent and levels of heavy metals including mercury, lead and copper were drastically reduced.
Of 33 native fish species once common along the length of the Seine, three were occasionally spotted near Paris by the 1960s. Today the number is around 26.
So confident were Paris city authorities of the quality of tap water last year - half of which comes from the Seine - they were miffed when a survey revealed half the city's population bought the bottled stuff.
To mark World Water Day, they handed out thousands of specially-designed "Eau de Paris" carafes for tap water to be kept cool in the fridge.
And for the past three summers, city officials have turned a 3km stretch of the Seine's right bank into an inner-city "Riviera", complete with sand, deck chairs and palm trees, although the river itself is not fit for swimming.
But the more Governments and scientists have battled to combat pollution in the Seine, the more complex the problem appears to be.
The Seine Normandy Water Agency is trying to convince farmers to reduce agricultural run-off but, as one of the most politically powerful lobby groups in France, they are virtually exempt from the polluter-pays system.
"The failure of our system is farming pollution," Bommelaer says, "but it's not easy to say to farmers, you must change. They are highly indebted, there are few rich farmers."
The agency has taken a softly-softly approach, running pilot projects on "green" farming, but nitrate levels in the lower Seine, caused from fertiliser run-off, remain stubbornly high.
Nitrates from fertiliser run-off help clog waterways by producing algal blooms which clog waterways and reduce oxygen levels in water.
Nitrate levels in the Seine continue to rise, albeit at a decreasing rate. But another pollution problem is being tackled more ambitiously.
At a cost of around EU$3 billion ($5.27 billion), the Seine Normandy Water Agency is building a giant storage tunnel, capable of controlling the flow of more than 2 million cubic metres of contaminated urban runoff to prevent it flooding into the Seine during heavy rain. At 53km-long and 6m in diameter, it is to be finished by 2015.
"It's a huge project. When it rains the sewer sediment is flushed out into the river and the fish die," Bommelaer says.
It has taken almost 20 years to begin turning back the pollution tide in two of Europe's most important waterways.
After Sandoz, a sophisticated alarm system was built along the river to warn of industrial spills or shipping accidents.
Rhine water is checked every six minutes, 24 hours a day, with a sophisticated alarm system giving the Dutch four hours warning to shut down drinking water stations if a major pollution incident occurs.
With almost half Europe's chemical industry in the Rhine's catchment, no one is taking any more chances.By Anne Beston