Water pollution has risen across three continents, placing hundreds of millions of people at risk of life-threatening diseases like cholera and typhoid, warned the United Nations Environment Programme (UNEP).
The worrying rise in the pollution of surface waters in Asia, Africa and Latin America also threatens to damage vital sources of food and harm the continents’ economies, according to UNEP’s recently published Snapshot of the World’s Water Quality. By making access to clean water even more difficult, water pollution also threatens to breed further inequality, hitting the most vulnerable – women, children and the poor – the hardest.
Jacqueline McGlade, Chief Scientist with UNEP, said at the launch of the report during World Water Week, “The increasing amount of wastewater being dumped into our surface waters is deeply troubling. Access to quality water is essential for human health and human development. Both are at risk if we fail to stop the pollution. Luckily it is possible to begin restoring rivers that have already been heavily polluted and there is clearly still time to prevent even more rivers from becoming contaminated. It is vital the world works together to combat this growing menace.”
Population growth, increased economic activity, the expansion and intensification of agriculture, and an increase in the amount of untreated sewage discharged into rivers and lakes are the main reasons behind the troubling rise in surface water pollution in Asia, Africa and Latin America.
Pathogen pollution and organic pollution rose in more than 50% of river stretches from 1990 to 2010 on all three continents, while salinity pollution has risen in nearly one third, the report finds.
Severe pathogen pollution, the rise of which is largely down to the expansion of sewer systems that discharge untreated wastewater into surface waters, is estimated to affect up to one-half of Asian river stretches, around a quarter of Latin American river stretches, and around 10 to 25% of African river stretches.
In some countries, more than 90% of the population relies on surface waters as their source of drinking water. These polluted waters — which are also used to prepare food, to irrigate crops and for recreation — pose a major threat to human health.
About 3.4 million people die each year from diseases associated with pathogens in water, like cholera, typhoid, infectious hepatitis, polio, cryptosporidiosis, ascariasis and diarrhoeal diseases. Many of these diseases are due to the presence of human waste in water.
UNEP estimates that up to up to 134 million people in Asia, up to 164 million in Africa and up to 25 million people in Latin America are at risk of infection from these diseases.
The solution is not only to build more sewers but to treat wastewater.
Severe organic pollution, which is caused when large amounts of decomposable organic compounds are released into water bodies, now affects around one out of every seven kilometres of all river stretches in Latin America, Africa and Asia. This type of pollution can lead to the complete lack of oxygen in water bodies, posing a major threat to freshwater fisheries that provide humans with the sixth most important source of animal protein and, in developing countries, employ 21 million fishermen and create 38.5 million related jobs.
Severe and moderate salinity pollution already affects around one-tenth of all river stretches in Latin America, Africa and Asia. High salinity levels, which occur when humans dump salty wastewater from mines, irrigation systems and homes into rivers and lakes, make it even harder for the world’s poorest farmers to irrigate their crops. Salinity pollution has increased between 1990 and 2010 in almost one-third of all rivers on the three continents.
Agriculture has intensified and expanded as the world seeks to meet the growing food demands of a booming population. This has led to an increase in the amount of phosphorus from fertilisers and pesticides that pollute water bodies. The resulting eutrophication – or the depletion of oxygen in a water body – can lead to a boom in weeds and algal blooms, as well as changes in the ecosystem and fish species.
More than half of the total phosphorus loads in 23 out of 25 major lakes worldwide are from human sources – inorganic fertiliser, livestock waste and human sewage. Most of the major lakes in Latin America and Africa now have higher levels of phosphorus than in 1990.
Among the rivers studied in detail for the report is the Godavari, India’s second longest river and third largest river basin.
The researchers found that in this basin, discharge of untreated and partially treated sewage from cities is one of the principal reasons why it failed to meet Indian water quality criteria. At several locations, the water quality of the Godavari does not meet the required criteria for Class A (“Drinking Water Source without conventional treatment but after disinfection”) including for biochemical oxygen demand (BOD). The chart below summarises the long term trend of BOD from several monitoring stations in the river. While there is a variation in the peaks, mean BOD levels are more or less constant.
Caption: Trend in biochemical oxygen demand (BOD) in the Godavari from 2002 to 2011 (Source: Central Pollution Control Board, Government of India)
Discharge of untreated and partially treated sewage from cities is one of the principal problems. The sources of water pollution include domestic sewage, industrial effluent, and agricultural non-point sources. More than 441 towns, 58,072 settlements and 33 cities are located in the basin area.
In Andhra Pradesh (situated in the lower Godavari basin), there are many sugar and distillery units, pulp and paper and fertiliser companies. The report quotes the Indian Central Pollution Control Board to say, “These industries are likely to be massive water consumers and contributors to the deterioration in water quality in the river particularly from Nashik to Nanded in Maharashtra and at Bastar in Chhattisgarh and Burgampahad in Andhra Pradesh.” Pollution due to the runoff of chemical fertilisers is also likely to be a problem. The average annual use of chemical fertilisers in the basin area is 49.34 kg per hectare, which is more than twice the national average. The total consumption of pesticides is 21,586 tonnes per year.
Following their study, the UNEP researchers say that the water quality index used for rivers all over India is based on concentrations and does not account for the adequacy of river flow for diluting wastes and supporting the aquatic ecosystem. It would be useful, therefore, to introduce minimum “environmental flows” as an additional benchmark for tracking the health of the Godavari.
The researcher found the Godavari particularly polluted along Nashik. They recommended a detailed pollution inventory and water quality control measures.
Overall, the report says, “There is a need for conducting comprehensive impact assessment going beyond the assessment of in-stream water quality. Such an assessment should cover the entire river basin ecosystem. For a holistic impact assessment, parameters such as water use (domestic, industrial agricultural) non-point pollution loads, agricultural yield, public health indicators, groundwater quality, ground water levels, biodiversity and top soil contamination should be considered, including climate change related vulnerability.”
The report says there is still time to tackle water pollution. Better water monitoring, especially in developing countries, is needed to understand the scale of the challenge around the world and to identify key hotspots. Once in-depth assessments have been done there are many new and old methods that can help to reduce the pollution at source, treat polluted water before it enters water bodies, recycle wastewater for irrigation and protect ecosystems by, for example, restoring wetlands to remove pollutants from urban or agricultural run-off.
“There is no doubt that we have the tools needed to tackle this growing problem,” said McGlade. “It is now time to use these tools to combat what is slowly becoming one of the greatest threats to human health and development around the world.”