But that has changed now that rivers pass through thickly settled landscapes — like the Ganges in India. And flow in the middle of industrial zones — like the Rhine. In modern times, rivers acquire toxic loads of biological and chemical wastes.

The Ganges: polluted as of 1886

The Ganges drains a quarter of India. Its basin in 1900 contained about 100 million people, of whom perhaps 10 million dumped their wastes directly into the river. The Ganges' fetid condition gave rise to one of the world's first antipollution societies, all the way back in 1886.

In 1990 as in 1900, almost all the sewage reaching the Ganges went untreated. Its decay robbed the river water of oxygen, menacing fish populations.

Mark Twain, who traveled the Ganges in 1896, found the water at the city of Varanasi (Benares) "nasty" on account of the "foul gush" of its sewers. A century later, by 1990, 450 million people lived in the basin — and some 70 million discharged their wastes into the Ganges.

Almost all the sewage reaching the Ganges, in 1990 as in 1900, went untreated. Its decay robbed the river water of oxygen, menacing fish populations with suffocation.

Religious pollution

The Ganges, because of population growth, suffered probably five to ten times more from biological pollution at the end of the century than at the beginning. The same must be true of hundreds of rivers around the world.

But the Ganges is unique in one respect. It acquired pollution for sacred as well as profane reasons. In Hindu belief, gods created the Ganges to give people a chance to wash away their sins.

Swimming with the dead

Hindus believe that death or cremation at Varanasi ensures liberation of the soul. So Varanasi attracts millions of elderly and sickly Indians. In the 1980s, Varanasi's official crematoria burned 30 million bodies a year — and deposited several million tons of human ash into the Ganges every month.

As cities and population grew, urban wastes affronted sensitive souls. No power, divine or not, did much to wash the filthy waterways.

Many additional bodies, partly cremated or not at all — given that fuelwood often costs too much — were shoved into the river, as were roughly 60,000 animal carcasses.

The Ganges was a bacteriological nightmare when the first systematic pollution studies took place in the 1960s. It then got worse. Government clean-up efforts, begun in the 1960s and coordinated into the Ganga Action Plan in 1985, had little discernible effect.

Cleansing the soul

In the case of the Ganges, the important changes were the creeping intensification of bacteriological pollution, not problems derived from industrial emissions, which the river's huge flow masked until about 1990. Bathing in the Ganges may cleanse the soul — but, now more than ever, not the body.

For rivers in the industrialized world, the situation was the opposite. Chemical pollution, derived from technological change and economic growth — not from population growth — menaced those rivers and lakes. The Industrial Revolution had a profound impact on the waters of the Western world.

The Rhine: an industrial waterway

Countless watercourses became variations on this theme. The story of the Rhine may stand for many other rivers.

French mining in Alsace sharply increased the salt content of the Rhine, jeopardizing the Dutch flower business.

The Rhine flows about 1,300 kilometers from the Swiss Alps to the North Sea. Before 1765, it flowed unobstructed. Its waters were clean enough to accommodate sensitive fish such as salmon, which were so plentiful that servants complained about having to eat it too frequently.

As cities and population grew, urban wastes affronted sensitive souls. No power, divine or not, did much to wash the filthy, frothy Rhine for a century and a half. After 1880, mounting chemical pollution added to the mix.

Attracting industry

The proximity of coal and iron deposits in the Ruhr valley assured that the middle Rhine would, in the nineteenth century, become an industrial zone. By the 1890s, its iron and steel production was very competitive worldwide, and production levels climbed further.

Salmon was so plentiful that servants complained about having to eat it too frequently.

The Rhine's suitability for navigation — its flow is very steady throughout the year — attracted other industries, including the formidable German chemical industry. By 1914, the Rhine's pollution load was heavy, salmon were rare.

Overly salty water

French potash mining in Alsace helped sextuple the salt content of the Rhine between 1880 and 1960. This in turn jeopardized the Dutch flower business, which irrigated its orchids and gladioli with Rhine water.

Nutrient loading with phosphorus and nitrogen — from detergents, sewage and fertilizers — emerged as an additional problem after 1948. It stimulated algae growth to the point that it clogged pumps and interfered with shipping.

International agreements

Clean-up efforts began with sewage treatment after World War II. In 1964, Germany required biodegradable detergents. International accords concluded among Germany, France and Holland restricted many forms of pollution from the 1970s onward. Most heavy-metal concentrations in the river, but not the sediment, declined sharply after 1975. Fish populations, in decline since 1885 and especially since 1915, rose after 1976. And fishermen on the Rhine caught salmon again in 1992.

© 2000 by J.R. McNeill.

Adapted from Something New Under the Sun. Reprinted