Tuesday 22 March is UN World Water Day, and the theme this year is “Groundwater – Making the invisible visible”. Water quantity issues tend to grab media attention – floods and droughts are often dramatic and visible in terms of their impacts on society. Like water below ground, water quality issues are often unnoticed; but global water pollution represents a major ‘invisible water crisis’ that we must address to help ensure the world’s population can have access to clean, safe water for sustainable development (UN Sustainable Development Goal 6).
The ‘water quality crisis’: three phases of river pollution
Healthy rivers provide vital services for humans and other life on Earth. Water pollution can seem like a 20th-century problem: solved and sorted. In reality, gains in water quality have been hard-won and far from universal, with many pollutants persisting or even increasing. Without widespread awareness and action, growing anthropogenic pressures could threaten anew the integrity of our water resources.
Poor water quality remains a pervasive problem. Water pollution causes 1.8 million deaths each year and yields an additional critical burden of chronic diseases.Landrigan et al., 2018
Across Europe, 34% of the 130,000 water bodies surveyed in 2020 failed to meet “good” chemical status. Notably, 100% of rivers in England, Germany, Belgium and Sweden failed standards, and less than one-third of rivers met comparable ratings used in the USA (Kristensen et al., 2018). Moreover, deteriorating water quality is evident for Asian, African and South American rivers (UNEP, 2016). These reports demonstrate that we have not solved our water quality woes.
The current state of river water quality reflects a history of human development and governance. We propose river pollution can be seen in three historical ‘Phases’:
Contaminant types and mitigation methods
Phase 1: Chronic organic pollution and pathogens associated with limited treatment of sewage, exacerbated by a rapidly increasing population density.
Phase 2: Point-source and diffuse pollution associated with the intensification of primary (agriculture, mining, forestry) and secondary (textiles, manufacturing, petroleum refining) industry.
Phase 3: Emerging contaminants associated with industrial (per- and poly-fluoroalkyl substances, nanomaterials), medical and veterinary (pharmaceuticals) advances.
In upper income countries, these Phases occurred over several decades or even centuries, tracking industrialisation and technological advances. This enabled development of infrastructure such as wastewater treatment facilities and capacity to monitor and regulate contaminants in Phases 1 and 2. Today, many lower- and middle-income countries (LMICs) are facing pressures from compressed and overlapping water pollution phases. Sanitation challenges from rapid urbanisation coincide with industrial development fueled by outsourcing of manufacturing and agriculture from UICs to LMICs. With even the highest income countries struggling to reduce Phase 2 and 3 pollutants, it is unsurprising that many countries lack the resources to address the multiplicative pressures of all three Phases simultaneously.
‘Invisible’ but impossible to ignore
With water technologies at an all-time high, what accounts for this lack of progress and even degradation of water quality worldwide? While water quantity challenges have attracted attention due to their visually dramatic manifestation (floods, drought), water quality issues are often inconspicuous or invisible. Several converging factors are making the three Phases of water pollution increasingly visible and impossible to ignore:
We are polluting more rapidly and diversely than ever
Thousands of pollutants now exist at detectable concentrations in the environment. Agricultural applications (fertilisers, pesticides, pharmaceuticals) are increasing worldwide, and freshwater environments are affected by salinization due to irrigation and sea level rise. Meat consumption continues to increase, with its associated nutrient and pharmacological burdens. Surges in pollution are generated by unforeseen global crises, such as plastic pollution linked to personal protective equipment against COVID-19 (Prata et al., 2020).
Environmental change and globalisation are focusing impacts of pollution in space and time
Land use and climate change are short-circuiting the water cycle (Levia et al., 2020). Extreme storms and altered surface and subsurface drainage accelerate pollution transport and reduce ecosystem removal processes. Moreover, human disturbance can result in long-term release of legacy contaminants (Van Meter et al., 2018). At the same time, abrupt increases in global trade have supercharged global transport of livestock, crops, manufactured goods, and waste. This has resulted in imbalances in nutrients, metals, plastics, and other contaminants. As LMICs, typically have less capacity to treat waste, this results in more water pollution per tonne and much higher human exposure.
Growing pollutant knowledge has improved regulation with more stringent standards
Although the widespread detection of long-banned pollutants such as PCBs could signal worsening pollution, often it reflects improved measurement capabilities. Sensitive methods now detect a wide array of pollutants at low concentrations. In some cases, our failures are a consequence of better-informed and increasingly stringent standards rather than absolute decreases in water quality.
From crisis to solutions
The last two centuries of water problems and solutions demonstrate that we must be proactive in managing river pollution rather than create new pollution legacies for future generations. In the face of intermeshed phases of pollutants, we need compressed and overlapping solutions that:
Integrate understanding of human activity into holistic water management
To address complex water quality challenges, rivers and their hinterlands must be managed as connected systems. This requires improved understanding of linkages between human activities on the landscape and water quality across space-time scales. Knowledge of water science is needed to balance public expectations and inform policy. Short-term interventions may take decades to result in improvements, while mismanagement may trigger new issues far into the future (Van Meter et al., 2018).
Move beyond regulating individual chemicals
To date, most chemicals are regulated individually. This can initiate a legislative wild-goose chase whereby slight changes to chemical composition circumvent regulation. A new EU model is emerging whereby chemicals are regulated based on their combined impact, as opposed to individual compounds. For this approach to be effective for more emerging contaminants, we need improved knowledge of potential acute and chronic toxicity of multi-contaminant cocktails.
Leverage long-term and novel data sources
Environmental regulation has been informed by manual sampling and in situ monitoring. Insights from satellite imagery and unoccupied aerial vehicles are expanding monitoring in inaccessible areas, enabling detection of sources and consequences of pollution (Huang et al., 2018). Yet, there is a parallel need to extend long-term monitoring to track progress and ground-truth newer methods. However, these records’ integrity is threatened by declining funding for monitoring networks, inconsistent approaches to data collection and lack of open data sharing (Lovett et al., 2007). A combination of conventional and cutting-edge monitoring methods is needed.
Engage and empower communities and decision-makers
Working directly with impacted communities to monitor water quality improves observational capabilities and empowers local people (Nardi et al., 2021). Stakeholder engagement and citizen science initiatives can lead to improved decision-making and behavioural change.
Share knowledge to boost human wellbeing
If knowledge and management actions are aligned with well-designed, effectively implemented and enforceable regulations, we can illuminate invisible water challenges, producing healthier river environments for the benefit of ecosystems and society.
This article is an abridged version of the paper published in Hydrological Processes (16 February 2022).