Water Quality and Pollution: Causes, Parameters, and Impacts

Water is fundamental to life, yet the quality of water we depend on is under serious threat. From rivers carrying untreated sewage to industrial effluents seeping into groundwater, water pollution has become one of the most pressing environmental challenges worldwide. Understanding how we measure water quality – and what degrades it – is the first step toward protecting this vital resource. This post covers the key parameters used to assess water quality, the major sources of pollution and their effects, India’s efforts to clean the Ganga River, and the complex issue of pollution that crosses national borders.

Parameters of water quality 🔗

Water quality is not a single measurement – it is evaluated through a combination of physical, chemical, and biological parameters. Physical parameters include colour, taste, odour, temperature, turbidity, and electrical conductivity, while chemical parameters cover pH, dissolved oxygen, hardness, and biochemical oxygen demand. Together, these indicators tell scientists and policymakers whether water is safe for drinking, aquatic life, agriculture, or industrial use.

Temperature 🔗

Temperature plays a surprisingly important role in water quality. It directly affects the metabolic rates and growth of aquatic organisms, the rate of photosynthesis in aquatic plants, and – critically – how much oxygen water can hold. Warmer water holds less dissolved oxygen than cooler water. This means that during hot summers or in stretches of rivers receiving heated industrial discharge (known as thermal pollution), oxygen levels can drop to levels that stress or even kill aquatic life. Temperature also influences the rate of chemical reactions and can make certain pollutants more toxic.

pH 🔗

The pH scale, ranging from 0 to 14, measures how acidic or alkaline water is. A pH of 7 is neutral. Natural water in the United States typically falls between 6.5 and 8.5 on this scale. Most aquatic organisms need a pH range of about 6.5 to 8.2 to survive. When pH drops too low (becomes acidic), heavy metals such as cadmium, lead, and chromium dissolve more readily, making water far more toxic. Conversely, higher pH can turn otherwise harmless compounds like ammonia into serious threats for fish and other organisms. Sources of pH changes include acid rain, mining runoff, and industrial discharge.

Turbidity 🔗

Turbidity refers to the cloudiness of water caused by suspended particles such as clay, silt, organic matter, and plankton. It is measured in Nephelometric Turbidity Units (NTU) using a device called a nephelometric turbidimeter. High turbidity is more than just an aesthetic problem. Suspended particles absorb more solar heat, which raises water temperatures and reduces dissolved oxygen. They also block sunlight from reaching submerged plants, slowing photosynthesis and further reducing oxygen production. Additionally, turbidity can damage fish gills, reduce growth rates, and act as a carrier for heavy metals and harmful microorganisms.

Dissolved oxygen 🔗

Dissolved oxygen (DO) is widely considered one of the most important indicators of water health. Higher concentrations of dissolved oxygen generally indicate better water quality. Oxygen enters water through direct absorption from the atmosphere, wind and wave action, and photosynthesis by aquatic plants. It is consumed by bacteria decomposing organic matter and by the respiration of aquatic organisms. When DO levels fall below 3 mg/L, most aquatic organisms experience significant stress, and the majority of fish cannot survive at levels of 1-2 mg/L. Factors that deplete DO include warm temperatures, excessive nutrient runoff (which fuels algal blooms that consume oxygen as they decompose), and the discharge of organic-rich sewage into waterways.

Hardness 🔗

Water hardness refers to the concentration of dissolved minerals, primarily calcium and magnesium. Hard water is not typically a health hazard, but it can cause scaling in pipes and boilers, reduce the effectiveness of soap, and affect industrial processes. From an ecological perspective, water hardness interacts with other parameters – for example, higher hardness can reduce the toxicity of certain heavy metals to aquatic life. Water is generally classified as soft (0-60 mg/L calcium carbonate), moderately hard (61-120 mg/L), hard (121-180 mg/L), or very hard (above 180 mg/L).

Water pollution and its impacts 🔗

Water pollution occurs when harmful substances enter water bodies faster than the environment can break them down or dilute them to safe levels. The sources are broadly categorised into three types: domestic, industrial, and agricultural. Each brings a distinct set of contaminants and health risks.

Domestic pollution 🔗

Household sewage is one of the largest contributors to water pollution, particularly in developing countries where treatment infrastructure is limited. Untreated sewage introduces pathogens – bacteria, viruses, and parasites – into rivers, lakes, and groundwater. This leads to waterborne diseases such as cholera, typhoid, dysentery, and hepatitis. Sewage also adds high levels of organic matter, which bacteria decompose using dissolved oxygen. This process, measured as Biochemical Oxygen Demand (BOD), depletes the oxygen available for aquatic life. In densely populated areas without adequate sanitation, domestic sewage can turn entire river stretches into what are essentially open drains.

Industrial pollution 🔗

Industries discharge a wide range of pollutants including heavy metals (mercury, lead, cadmium, chromium), chemical solvents, oils, and thermal effluents. These substances can be acutely toxic to aquatic organisms and enter the food chain, eventually affecting human health. Bioaccumulation – the process by which toxic substances concentrate as they move up the food chain – means that even low concentrations in water can result in dangerous levels in fish and other organisms consumed by humans. The Minamata disease in Japan, caused by mercury-contaminated industrial discharge, remains one of the starkest examples of industrial water pollution harming human populations.

Agricultural pollution 🔗

Agricultural runoff carries fertilisers (rich in nitrogen and phosphorus), pesticides, herbicides, and animal waste into waterways. Excess nutrients trigger a process called eutrophication – explosive growth of algae that blocks light, depletes oxygen as it decomposes, and creates “dead zones” where aquatic life cannot survive. Pesticides in water have been linked to disruptions in endocrine systems of wildlife and potential health risks for humans, including increased cancer risk with long-term exposure. Agricultural pollution is often classified as non-point source pollution, meaning it does not come from a single identifiable pipe or discharge point, which makes it particularly difficult to regulate and control.

Health effects of water pollution 🔗

The health consequences of water pollution are severe and disproportionately affect communities in developing nations. According to the World Health Organization, contaminated water and poor sanitation are linked to diseases such as cholera, diarrhoea, dysentery, hepatitis A, and polio. Heavy metals in drinking water can cause neurological damage, kidney failure, and developmental problems in children. Nitrate contamination from agricultural runoff poses risks to infants through a condition known as methemoglobinemia, or “blue baby syndrome.”

The Ganga action plan: India’s river cleanup effort 🔗

The Ganga River – flowing over 2,500 km from the Himalayas to the Bay of Bengal – is one of the most culturally significant and heavily polluted rivers in the world. There are over 29 cities, 97 towns, and thousands of villages along the banks of the Ganga, and its basin supports over 500 million people. Rapid urbanisation, industrial growth, and agricultural expansion have caused massive amounts of untreated sewage, industrial effluent, and agricultural chemicals to flow into the river.

Origins and objectives of the plan 🔗

The Ganga Action Plan (GAP) was launched by then Prime Minister Rajiv Gandhi in June 1985, covering 25 Class I towns across Uttar Pradesh, Bihar, and West Bengal, with an expenditure of ₹862.59 crore. It was India’s first large-scale, government-led river cleanup initiative. The primary objective was to improve water quality by intercepting, diverting, and treating domestic sewage and preventing industrial waste from reaching the river. Additional goals included controlling non-point pollution from human defecation, cattle use, and the disposal of human remains in the river.

Phases and progress 🔗

The plan was carried out in two phases. Phase I ran from 1985 to 2000 and covered three states. Phase II began in 1993 and expanded to seven states, including Uttarakhand, Delhi, and Haryana. Out of 764 projects approved under Phase II, 652 were completed by 2014. However, despite these efforts, results were mixed. The National Green Tribunal observed in 2017 that even after spending over ₹7,300 crore, the quality of the Ganga had not significantly improved.

From GAP to Namami Gange 🔗

Recognising the shortcomings of the earlier plans, the Indian government launched the Namami Gange Programme in 2014, with a budget of ₹20,000 crore – five times the total spent in the preceding three decades. The programme adopted a more comprehensive approach, focusing on sewage treatment infrastructure, industrial effluent control, river surface cleaning, rural sanitation, afforestation, and biodiversity conservation. Between 2015 and 2021, 815 new sewage treatment plants were built or proposed, doubling the number that existed in 2015. The programme has been recognised as a World Restoration Flagship under the UN Decade on Ecosystem Restoration, and sightings of Ganga river dolphins and other wildlife have reportedly increased.

Challenges and lessons learned 🔗

Despite progress, challenges remain significant. Auditors have noted delays and deficiencies in implementation and monitoring. The rate of urbanisation continues to outpace the expansion of sewage treatment capacity. Cultural practices, open defecation near riverbanks, and weak enforcement all complicate the cleanup. The GAP’s experience has taught planners that top-down, end-of-pipe solutions are insufficient without public participation, long-term maintenance planning, and strong data on actual pollution loads.

Transboundary impacts of water pollution 🔗

Water does not respect political boundaries. When a river, lake, or aquifer is shared by two or more countries, pollution generated in one nation can cause severe environmental and health consequences downstream. This makes transboundary water pollution one of the most complex challenges in international environmental governance.

How pollution crosses borders 🔗

Pollution from one country can undermine the ability of neighbouring countries to use shared water resources and can trigger tensions within the basin. For instance, industrial effluent or agricultural runoff entering a river upstream can degrade water quality for millions of people in downstream nations. This has been documented in basins around the world – from the Mekong in Southeast Asia to the Euphrates-Tigris system in the Middle East. Transboundary waters account for 60% of the world’s freshwater flows, and 153 countries have territory within at least one of the 286 transboundary river and lake basins.

International legal frameworks 🔗

To address these challenges, the international community has developed two key legal instruments. The 1992 UNECE Water Convention (also known as the Helsinki Convention) requires parties to prevent, control, and reduce transboundary water pollution and to cooperate through joint bodies. Originally open only to UNECE member states, it was amended in 2003 to allow countries worldwide to join, and as of 2022 had been ratified by 47 parties. The 1997 UN Watercourses Convention establishes principles of equitable and reasonable use, the obligation not to cause significant harm, and requirements for notification and consultation. Together, these conventions – along with over 600 regional treaties – form the backbone of international water cooperation.

Transboundary river basin organisations 🔗

Practical cooperation often happens through transboundary river basin organisations (TRBOs). These organisations provide a framework for coordinating water management across international boundaries, with functions that include joint monitoring, data sharing, developing action plans to reduce pollution, and serving as forums for resolving disputes. Notable examples include the International Commission for the Protection of the Rhine (ICPR) in Europe, the Mekong River Commission in Southeast Asia, and the Volta Basin Authority in West Africa. The success of the ICPR is often cited – collaborative efforts led to pollution reduction targets being achieved by 2000, and salmon returned to the Rhine after a 50-year absence.

Challenges in transboundary cooperation 🔗

Despite the frameworks in place, progress remains uneven. Only 43 out of 153 countries sharing transboundary waters have operational arrangements covering 90% or more of their shared basins. Many developing regions, particularly in Asia and Africa, lack adequate institutional mechanisms. Power asymmetries between upstream and downstream nations, competing economic interests, data-sharing reluctance, and the growing pressures of climate change all complicate cooperation. As water demand increases and climate patterns shift, the need for robust transboundary water governance is only growing more urgent.

The road ahead 🔗

Water quality is not just a technical or environmental issue – it is a matter of public health, economic development, and international peace. Whether we are talking about the dissolved oxygen levels in a local stream, the industrial effluent flowing into the Ganga, or the pollution crossing from one country into another, the underlying challenge is the same: managing shared water resources responsibly.

Improving water quality requires action at every level – from investing in sewage treatment and enforcing industrial discharge standards to establishing effective transboundary cooperation agreements. It also requires monitoring, data transparency, and public participation. The lessons from the Ganga Action Plan, the success stories from the Rhine, and the ongoing challenges in shared basins worldwide all point to the same conclusion: protecting water quality demands sustained commitment, innovation, and collaboration.

What do you think? Can large-scale river cleanup programmes like the Ganga Action Plan truly succeed without fundamental changes in how cities and industries manage waste? And in an era of rising water stress, how should countries balance national development priorities with their responsibility to protect shared transboundary water resources?

References

1. https://sensorex.com/three-main-types-of-water-quality-parameters-explained/
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5. https://www.who.int/news-room/fact-sheets/detail/drinking-water
6. https://pmc.ncbi.nlm.nih.gov/articles/PMC7351670/
7. https://en.wikipedia.org/wiki/Pollution_of_the_Ganges
8. https://testbook.com/ias-preparation/ganga-action-plan
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11. https://www.thegef.org/newsroom/blog/making-water-source-peace-transboundary-cooperation
12. https://www.unwater.org/water-facts/transboundary-waters
13. https://en.wikipedia.org/wiki/Convention_on_the_Protection_and_Use_of_Transboundary_Watercourses_and_International_Lakes
14. https://waterknowledgehub.org/learn/iwrm-tools/transboundary-organisations