Water-related risks threaten society at the local, national and global scales in our inter-connected and rapidly changing world. Most of the world's poor are deeply water insecure and face intolerable water-related risks associated with complex hydrology. Most of the world's wealthy face lower water-related risks and less complex hydrology. This inverse relationship between hydrological complexity and wealth contributes to a divided world. This must be addressed if global water security is to be achieved. Using a risk-based framework provides the potential to link the current policy-oriented discourse on water security to a new and rigorous science-based approach to the description, measurement, analysis and management of water security. To provide the basis for this science-based approach, we propose an encompassing definition rooted in risk science: water security is a tolerable level of water-related risk to society. Water security policy questions need to be framed so that science can marshal interdisciplinary data and evidence to identify solutions. We join a growing group of scientists in asserting a bold vision for science leadership, calling for a new and comprehensive understanding of the planet's water system and society's water needs.
1. One blue planet: why water-related risks matter to society at all scales
Only the Earth appears from space as a blue planet—a vivid sign of water's ubiquity. The oceans dominate the Earth's overall water cycle (97.5%). Fresh liquid and atmospheric water, which sustains terrestrial life, is a small and fragile balancing item within a much larger system, constituting less than 1% of our water stock (excluding the 1.7% currently locked in ice). We know a great deal about many aspects of water within defined scales, from microscopic to the larger scale of basin boundaries and sovereign nations. We know very little about the global water cycle and its physical fluxes , whose boundaries are planetary, and whose interactions and impacts are environmental, social, economic and political. We know even less about how the global water cycle is being altered in our changing world, not least by climate change . The water-related risks our planet faces in the relatively near future are uncertain but are increasingly perceived as a major threat to society and the economy . The scale at which society has understood and managed water-related risk has extended remarkably over the past two centuries. This must now extend further, to include all scales, from local to global.
Historically, society has perceived the scale of freshwater risk to be primarily local—at the scale of human settlement and its immediate hinterland, where institutions and policy focused on reliable access to water supply, sanitation and irrigation services and water-related energy and transport services. Institutions—defined as rules, norms and the organizations that implement them—have grown in complexity to match multi-dimensional water challenges. Local responses have typically shifted from self-provision of services to community-based and then public and private approaches, although all of these still have their place in all societies today. Water management and services continue to be of primary importance at the local scale and getting institutional design right is a necessary (but insufficient) key to success. For those with adequate water services, costs are rising, with increasing energy prices, environmental concerns, water demand and rapidly growing cities. However, far too many people do not have adequate services: about 800 million people are without improved water supply, expending time and labour transporting water and risking health; about 2.5 billion people are without sanitary toilets, many defecating in the open, risking health and dignity; and about 900 million people are malnourished, with multiple associated risks . These numbers are a fundamental challenge for human development and a stark reminder of our divided world, which creates great risks for society. Recognition of this has underpinned the discourse on the human right to water.
Over the past century, the nation state and, within it, the river basin and local jurisdictions have become the scale at which institutions at different levels manage water-related development, risks and trade-offs. This has led to improved outcomes in many nations, in terms of health, productivity and ecosystem management, providing greater potential to manage the risks of variable systems. However, water-related risks remain very high and unmanaged in many nations. For example, in the summer monsoon of 2010, Pakistan faced “catastrophic flooding” , with 20% of its land area (the size of the UK) underwater, 20 million people seriously affected, 2000 people killed, 1.7 million homes destroyed and a US$20 billion economic loss. Serious floods returned in the 2011 and 2012 monsoons. Institutional and policy failure to cope with such risks has severe social and political consequences.
Although myths have dominated dialogues about the great rivers for millennia , only in recent decades have river basins and aquifers beyond the nation state become a unit of modern risk management and mitigation, although national sovereignty remains a fundamental principle governing international waters. While stable, cooperative institutional and policy regimes have been established in some international river basins, many of the most populous and geopolitically significant basins are contested. Examples include the Ganges sub-basin, inhabited by about 650 million people in four countries, with many governance responsibilities shared between federal states, and the Nile basin, inhabited by about 200 million people in 11 countries, with many more people within the countries but outside these basins who depend on the rivers in some ways. There are weak institutions in, and limited shared understanding of, these and many other river basins, resulting in misperceptions, fears, suboptimal development and associated political risks.
In a globalizing world, local water use is greatly influenced by patterns of trade and local water shocks can have global spillovers with major financial, economic and political impacts. For example, the 2010 Russian drought was the worst in a century, with a major drop in wheat production resulting in an export ban in August followed by an immediate spike in grain prices. Bread prices in the Middle East and North Africa, dependent on Russian grain imports, increased remarkably by the beginning of 2011. In February 2011, economist Krugman , p. A23 of the New York edn wrote that ‘there's little question that sky-high food prices have been an important trigger for popular rage’ and ‘what really stands out is the extent to which severe weather events have disrupted agricultural production’. Popular rage quickly led to regime change in Tunisia, Egypt and Yemen in 2011.
Also in 2011, massive floods and inadequate management responses in Thailand resulted in 884 deaths, 1.5 million homes and 7500 industrial plants damaged and 25% of the rice crop destroyed. The US$45 billion direct and indirect economic loss places these floods among the costliest natural disasters on record . The $15 billion insured loss has led to a ‘paradigm shift in the mindset of insurers’ . Global spillovers were numerous, owing to large-scale production losses in the critical parts of global supply chains. Computer prices spiked owing to shortages of computer hard drives (e.g. Western Digital production down by 51%—24 million drives). Motor vehicle production was similarly hit (e.g. Toyota production down by 260 000 vehicles—56% decrease in revenue, $2.3bn loss; Honda production in the USA down 50%, owing to parts supply chain failure) . These examples illustrate how local water-related risks and shocks and inadequate policy responses can have major global financial, economic and political spillovers. Yet, there are limited international mechanisms to monitor and respond to such spillovers.
While water-related risks continue to threaten society at the local, national and international scales, they now increasingly do so at global scales owing to rapid economic, demographic and climate change. While we are not ‘running out of water’, we urgently need to understand better how larger global changes will affect freshwater availability. Stationarity1  can no longer be assumed, and water and its associated interactions and impacts at local to planetary scale need to be understood. This requires that we move beyond the prevailing ‘water scarcity’ discourse and the comfortable scales of river basins and the nation state. Water does not respect borders and sovereignty, and the nation state can no longer provide the sole basis for water management. Managing water-related risks means achieving ‘water security’ at all scales to protect and conserve our ‘one blue planet’.
2. Water security and complexity in a divided world: a policy challenge for science
In recent years, the term ‘water security’ has become widely used and has been defined in many different ways .2 A widely cited and adapted definition of water security is ‘the availability of an acceptable quantity and quality of water for health, livelihoods, ecosystems and production, coupled with an acceptable level of water-related risks to people, environments and economies’ .3 This descriptive definition usefully distinguishes the productive role of water access (‘services’) from the destructive role of water-related ‘events’, including and beyond hydrological shocks (e.g. hostile destruction or contamination of water sources). Both roles can be described in terms of societal risk, i.e. risks associated with unreliable water services and with unpredicted water-related events. Using a risk-based framework provides the potential to link the current policy-oriented discourse on water security to a new and rigorous science-based approach to the description, measurement, analysis and management of water security . To provide the basis for this science-based approach, without replacing the policy-useful definition above, we propose an encompassing definition rooted in risk science: water security is a tolerable level of water-related risk to society.
Risk (a situation involving exposure to danger or threat) is offset by security (the state of being free from danger or threat). The concept of tolerable risk is an important idea in risk science, referring to a level of risk that is ‘as low as reasonably practicable’, describing the zone between unacceptable and acceptable that is both context and values dependent . Water-related risk includes risks of water-related events and risks to water services—examples of the ‘external’ risks and the ‘manufactured’ risks described in the work of Beck and of Giddens, which provides a valuable social science foundation (e.g. ). Society encompasses the individual, family, farm, firm, city, nation, region and planet; capturing all scales, needs and values (such as culture and ecosystems).
In defining water security as a tolerable level of water-related risk, it is clear that most of the world's poor people currently face intolerable water-related risk and are water insecure. Yet, they may need and choose to invest first in reducing other intolerable risks (e.g. of food and energy insecurity). Wealthy societies are predominantly water secure and do not need to make such choices. The scale of their investments in water institutions and infrastructure is a result of ‘satisficing’. This is a proxy measure for tolerable water risks, providing a potential water security metric derived from the analysis of when investments tail off as well as from established design thresholds (e.g. for service standards, flood risk, contaminant loads). Development of a risk-based framework for water security will inform the emerging international water security policy discourse, potentially providing it with required specificity. It will also inform the associated human rights discourse, which would seek a platform of normative goals for society. Such goals for water security are far from being achieved, underscoring the moral, as well as the political and economic, imperatives for action.
Water systems comprise complex interactions of physical, social, economic and political factors, including risks and uncertainties. They become more complex with ‘difficult hydrology’—defined by a mixture of natural aridity, flood vulnerability and high inter- and intra-annual rainfall variability, with the last being the most complex. Complexity increases the investment (in information, institutions and infrastructure) required for water security . Many of the poorest regions of the world are characterized by such hydrological risks and are least equipped to cover the comparatively high coping costs of infrastructure and institutional innovation. In parts of sub-Saharan Africa and South and Southeast Asia, the transition to a water-secure future is very costly and complex, which traps these regions in a low-level equilibrium. Today, the consequence is increasingly global spillovers of local and regional shocks.
With economic growth and changing ethics and standards in water-secure regions of the world, societal measures of tolerable water-related risk have changed. At the same time, twentieth century core solutions to water insecurity in these countries (e.g. large dams and flood management structures) are increasingly contested, because of their social and environmental trade-offs. Yet, the nature of the ‘Anthropocene’ age is that societies are creating new environments. The challenge is to move beyond simply protecting and conserving natural aquatic ecosystems and rather to ensure that these new physical environments are resilient, across the full range of societal goals.
Figure 1 divides the world into four quadrants in terms of: (i) hydrological complexity and (ii) investment levels to achieve tolerable levels of water-related risk. The quadrants on the left side of the plot have relatively low hydrological complexity—comparably easy hydrology marked by moderate rainfall and variability (quadrants I and II). These two quadrants are separated by the level of investment in risk reduction, which reflects differences in societal values and policy responses. Holding the level of hydrological complexity roughly constant, lower investments in risk reduction may represent fragile water security or a higher tolerance of water-related risk. This contrast is exemplified by the lower water quality standards in, for example, Northern China (quadrant II) than in Northern Europe (quadrant I).
The right half of the plot captures regions with more complex hydrological conditions. Western North America, Australia, Japan, Israel and South Africa have invested heavily in infrastructure and institutions matched to a more challenging environment. These regions (quadrant III) have enhanced but still fragile water security, despite hydrological complexity, in most cases partly as a consequence of relatively recent in-migration importing substantial public and private capital and capacity. Much of the world's poor is trapped in a low-level equilibrium in agriculturally dominated economies most vulnerable to hydrological complexity and least capable of meeting the exceptionally high costs of information, infrastructure and institutional investment required to cope (quadrant IV). Latin America and the Middle East and North Africa region (MENA region) straddle the divide between quadrants.
The information gap between the water-insecure regions (quadrant IV) and the rest of the world is startling. Analysis of complex systems requires a great deal of data and knowledge, and the associated costs and capacity required to acquire this is high. While some parameters, such as rainfall and evaporation, can be measured using remote-sensing or other innovative techniques, they still depend on field measurements for calibration. Measurement of other critical parameters, notably flow in rivers and groundwater stocks, still primarily use what have been described as ‘semi-artisanal methods’, although promising remote sensing tools have emerged over the past decade . Yet, without robust knowledge of the complex local relationships between rainfall, run-off and stream flow, it is difficult to model the behaviour of hydrological systems and then to negotiate and manage their use in the context of future challenges. As an example, despite huge investments in climate science, there is still very limited ability to project likely future changes in water resource availability as a consequence of climate change. These are areas where scientific innovation could have major impacts.
There is a paradox illustrated in figure 2, which maps stations that monitor rainfall  (not flows, whose recording is important but much less dense). Predominantly wealthy regions of the world with comparably easy hydrology have invested in strong institutions and substantial water infrastructure, including dense hydrometeorological networks—again a result of satisficing and thus an indicative measure of tolerable water risks. Poorer, water-insecure regions with ‘difficult hydrology’ have been unable to provide the exceptionally heavy investment required in water institutions and infrastructure. Consequently, they only have a small fraction of the data-monitoring density and institutional capacity for decision-making that they need to understand and manage their more complex systems. Figure 2 also illustrates a striking decrease in observational data coverage between 1989 and 2006 for most regions. Even as global change poses unprecedented challenges, the monitoring required to achieve tolerable levels of water risk is failing to keep up in the easiest hydrology, whereas the poorest remain left far behind. You cannot manage what you do not measure.4
Improved knowledge will reduce the burden of complexity, decrease the cost and increase the effectiveness of investments in improving water security, essential to move regions out of a low-level equilibrium. However, many of the data, frameworks, models and tools developed for the rich parts of the world with lower complexity (‘easy hydrology’; quadrants I and II) are either non-transferable or unavailable for regions with ‘difficult hydrology’. For example, standard economic modelling assumptions that smooth factors of production (and, implicitly, average rainfall) considerably overestimate economic growth projections in Ethiopia , when compared with growth projections accounting for the impacts of hydroclimatic variability, suggesting that such models need major refinement.
In the absence of advanced knowledge and shared understanding, complexity feeds poor decisions and associated tension. Policy miscommunications and misperceptions have serious consequences in a globalizing water environment. Poor understanding of river basins and aquifers in poorer, water-insecure regions exacerbates local and regional impacts and associated global spillovers. Misperceptions and fears constrain and even preclude the international relationships required for wider economic development and benefit sharing, to create positive-sum outcomes that will contribute to political and economic stability .
This inverse relationship between hydrological complexity and economic growth must be addressed if global water security is to be achieved 22. This is a prerequisite for managing social, political and business risks in our changing world. Science can and must provide innovative tools to advance the level of knowledge of complex water systems and identify innovative solutions to manage such systems.
3. A paradigm shift in policy-driven science
Water security must cope with complexity, but policy-makers want certainty. An analyst noted that ‘science without policy is simply science; while policy without science is gambling’. Effective science–policy dialogue has become more important—yet more difficult—in a globalizing context. Water security policy questions, to contain and manage water-related risks from the household to the global level, need to be framed so that science can marshal interdisciplinary data and evidence to identify solutions. This agenda must overcome hitherto intractable incentive problems for scientists, who are not rewarded for taking risks and for working across disciplinary or science–policy divides, in a world where national sovereignty and data secrecy commonly prevail in water-related matters.
(a) The trillion dollar water security policy challenge
The twenty-first century water security policy challenge over the next generation is to ensure tolerable water-related risks to society, at all scales, everywhere. This overarching challenge requires
(i) Ensuring efficient water-related services for 9 billion people: addressing a series of defining water challenges for science and society, including: efficient water and sanitation services for 7 billion people and industries in cities (e.g. ‘water conservation and recycling’ and ‘toilets without water’) and 2 billion in rural settlements; food for 9 billion people (e.g. ‘optimizing water use for food production’); conservation of water in energy production and energy in water services (e.g. ‘water-energy nexus’); and sustainable ecosystem services (e.g. ‘water–nature in balance’).
(ii) Managing water-related threats to society: managing water quantity and quality, and shocks and tipping points and their spillovers requires interdisciplinary and comprehensive knowledge of water and its relationship to society, at all scales. This requires both basic and applied science, including: consensus on global data architecture, metrics, modelling platforms and monitoring systems; analysis of water services, water shocks and spillovers; identification of future scenarios and their management options on a generational time scale; effective design of early warning systems that reach everyone at risk across the planet, regardless of national, cultural and language boundaries; and institutional innovation, drawing particularly from smaller scale successes with management of the commons, and identifying new approaches to governance appropriate for complex issues in an increasingly networked world. This will enable the fundamentally important analysis of envelopes of tolerable risks and their trade-offs, to inform policy and practice, including that of government, business and individual actors.
(b) The science response to the policy challenge
The response of the global science community to the water security policy challenge requires a water-centred systems perspective on the complex, interconnected risks facing society. We join a growing group of scientists  in asserting a bold vision for science leadership, calling for a new and comprehensive understanding of society's water needs and the planet's water system, with a clear pathway to public and private decision-makers. This requires harnessing unprecedented access to extensive digital water data, massive computing power and advanced modelling skills and platforms. The water security policy challenge establishes principles and priorities for four areas of action by the science community:
(i) Establish a global architecture to work across disciplines and science–policy divides. The complexity of water security challenges requires systems thinking to understand interdependent risks and uncertainties at all scales. The challenge for science is to mobilize the data and information required to develop a global systems perspective that can underpin a unifying risk-based framework for water, linking the hydrological and socioeconomic dimensions of water from the household, the firm and the farm to local, regional and global water fluxes. A global architecture refers to shared language, frameworks and tools, including metrics, data standards, benchmarks and science networks. This is required to bridge across disciplines that use different concepts and languages to examine similar problems. These globalized frameworks, datasets and modelling platforms are a prerequisite for understanding the world's water system and to provide a foundation for the resolution of complex challenges at all scales.
(ii) Fill the water knowledge gap and ensure knowledge flow at local to global levels by harnessing the information technology revolution. In shared river systems, technological innovation in remotely sensed, open-access, digital water data and information systems has the potential to replace myths and perceptions with knowledge that transcends physical boundaries and disparities in data density, and to inform policy and trade-offs. Revolutions in mobile data, crowd sourcing, social networks and citizen science empower traditionally disenfranchised regions, science communities and civil society. Information technology and communication innovations facilitate the coevolution of scientific research communities and institutions required to identify and adopt best practice. The development and deployment of innovative tools can greatly enhance monitoring of critical parameters such as stream flow and groundwater storage, whereas new decision support and other modelling tools can equip networked governance across scales and sectors, enabling ‘real-time’ decisions that address pressing water issues that face society.
(iii) Overcome disincentives for interdisciplinary and international water science. Interdisciplinary water-related science must overcome seemingly intractable obstacles to cooperation. Publishing conventions, research-funding schemes and career paths in academia pose stubborn barriers to progress. Overcoming these obstacles requires new models of policy-engaged scientists, creative academic career paths, entrepreneurial research-funding schemes expanding beyond traditional government funding, and cooperative programmes that bring together research institutes, development organizations, business and governments.
(iv) Act on the priority science agenda now and let intergovernmental action follow. Air transport and shipping; infectious diseases; trade; crime; meteorology and weather forecasting; climate change—are all examples where global agreements and mechanisms have been established to manage potentially intolerable risks perceived by wealthy nations. Because water security challenges are complex and locally diverse, they are not adequately recognized or prioritized as policy challenges by most wealthy and currently water-secure nations. This explains the absence of specific global mechanisms to promote cooperation in water security monitoring, analysis and governance. Significant action is unlikely to be initiated through intergovernmental consensus mechanisms in the short term. Scientists have the obligation to recognize the policy challenge described here, and to move forward with building the evidence and knowledge base, catalysing the establishment of the global (and eventually intergovernmental) architecture required for water security.
This review sets out the importance of water security for society at all scales, considering water security from a risk–science perspective. In setting out the policy challenge across a complex and interconnected world, we outline policy-driven questions to drive science and innovation and describe the barriers that must be overcome. This call for action demonstrates the need for a journey by a coalition of willing and capable scientists, working in concert with governments, business and civil society to address the systemic and pressing water security challenges that face our society.
This journey has begun. Cutting-edge examples of water-related systems analysis are increasing in number. Geoscientist Famiglietti  has identified the North American freshwater science agenda in National Geographic. The International Institute for Applied Systems Analysis is developing a new systems approach to water scenario futures. As an international example for the developing world, strategic basin assessments supported by the World Bank have linked hydrological modelling and economic optimization to dispel stubborn myths and misconceptions in several contested river basins. The 2012 Oxford Water Security Conference  established a coalition of interdisciplinary scientists and practitioners examining selected river basins as complex systems and identifying dominant risk factors, tipping points, trajectories and management options to enhance water security.
These are important but as yet insufficient steps. The scale of the water security challenge is unprecedented. Our current knowledge of the interconnected global water system and its changing fluxes is inadequate. Everywhere and at every scale, the risks to society of the impacts of change on water security are potentially very high. However, these risks can be reduced and managed with knowledge and concerted action. The science and policy communities collectively need to respond in a bold, determined and coordinated approach to lay the foundations for universal water security within our ‘one blue planet’.
One contribution of 16 to a Theme Issue ‘Water security, risk and society’.
- © 2013 The Author(s) Published by the Royal Society. All rights reserved.