For decades, human beings have treated many of the planet’s rivers as sewers. Yet, ironically, those rivers to have suffered most the pollution effects were originally chosen as a backbone, a source of wealth, of new urban settlements and industrial enclaves.
Waste tips, deforestation, pesticides used in farming, sewage… the causes of water pollution are diverse and all the result of human intervention. In this article, we will find out the planet’s most polluted rivers and the main causes of what can only be seen as environmental disaster on a global scale.
But, before we explore the theme further, let’s look at some statistics and the important concepts about rivers pollution:
Half of Asia’s river reaches, a quarter of those in Latin America, and between 10% and 25% of those in Africa, are affected by some kind of pollution. A closer look reveals this to be a problem afflicting developing countries and the poorest part of the population, who source directly from water courses to drink or cook with.
Despite “Clean water and sanitation” being one of the Sustainable Development Goals(no. 6), and the United Nations continuing to work to guarantee access to drinking water for everyone, around 1,000 children die every year from preventable diseases related to water and sanitation.
According to the UN, 80% of sewage water is released into the environment without any treatment whatsoever. The processes of eutrophication, which is characterized by a disproportionate increase in nutrients such as phosphorus produced by fertilizers, pesticides or animal feces, change the structure of the rivers and their ecosystems, and affect the biota that lives inside them. This is just one of the causes of the pollution problem drowning our rivers. Wasterwater treatment systems could in many cases be a solution to this problem.
Let’s now look at the most contaminated rivers on the planet:
Yamuna, tributary of the Ganges
India is the world’s most polluted country and, as such, its most important river is no less so. The Ganges has become a big waste dump over which animals and human bodies are incinerated, and thousands upon thousands of pilgrims bathe to cleanse their sins.
One of its tributaries, the Yamuna, is the most polluted urban river in the world. Its water is anoxic, i.e. it has zero oxygen, is pure feces, and cannot support any kind of aquatic, plant or bird life. Only when you get 200 km downstream does it start to recover.
Located in South-East Asia, the Salween, born in Tibet, meanders down through regions of China and Burma. Over its course, it passes through industrial parks, mostly made up of textile factories, whose polluting waste have provoked an alarming increase in sulfur, cadmium, copper, lead, mercury and zinc levels in the river. The Salween is considered the most polluted river on the planet, so much so that some fishing communities have abandoned their former trade to sell on the glass and plastic they collect from the river.
Tipping of industrial waste and by neighborhood communities is an incessant source of pollution in River Plate, the second biggest water course in South America. The sluicing of the water with chemical waste from farming activities has also increased in recent years, another reason it is included in the list of most polluted rivers on the planet.
The causes of water pollution in the Danube, one of the few European rivers to appear on the list, are similar to those in many of the other rivers included. Chemical waste is its great enemy, not just farming pesticides, but waste from Serb factories bombarded as of 1999. Increasing river traffic is another factor in the river’s growing contamination.
The volume of the Río Grande, the second biggest water course in the United States, is fallling every day due to water extraction for agricultural and domestic use. The Río Grande flows through a region increasingly afflicted by drought and proliferation of invasive species that consume a lot of water. Its basin is also increasingly polluted by industrial tipping.
Autochthonous species in the Murray-Darling River, one of the most important in Australia, have plunged to 10% of their levels prior to European settlement. Invasive species, on the other hand, have significantly jumped in number. This has caused an imbalance in its biodiversity that has left nine native species in danger of extinction, affecting aquatic flora and water quality.
Pakistan’s main river is in grave danger as a consequence of climate change, since most of its water depends on flows from glaciers. With global warming, much of the glaciers have dried up and thus cannot feed or moderate the river, and this environmental problem is set to increase in the future.
Added to this is the constant extraction of water for farming activities, causing the incursion of salt water into the delta, wiping out part of its natural biota.
Water extraction from the River Nile, for irrigation, is now so high that, despite its huge size, the river doesn’t reach the sea during dry periods. It is also likely that salt water incursion in coastal areas is growing, as a result of the rising sea level due to global warming, and the availability of freshwater continues to decline in the delta region.
This not only brings huge problems for species living in its waters, but the variations in volume, in a river that crosses more African countries than any other, cause geopolitical tensions and insecurity around the issue of water management.