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Despite a 5,000-yr-long history of water governance1, the world’s first global conference on water2 was not held until 1977 in Mar del Plata (MDP), Argentina—the United Nations (UN) Water Conference (Fig. 1). MDP was the first gathering of governments at a high political level to respond comprehensively to multiple global water agendas3. Its focus was to ensure that all people, irrespective of their state of development and social and economic conditions, had access to water in the appropriate quantity and quality to cover their basic needs4.

Fig. 1: Timeline of key UN water-related initiatives between 1975 and 2030.
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The interval between the first and second UN Water Conference was 46 years. Over this time key global initiatives have included the Millennium Development Goals (2000–2015) and most recently, the Sustainable Development Goals (2015–2030).UNCED, United Nations Conference on Environment and Development (also known as the Earth Summit). ICWE, International Conference on Water and the Environment.

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The MDP water agenda was carried forward in the International Conference on Water and the Environment in Dublin (1992) and the World Summit on Sustainable Development in Johannesburg (2002). Multiple UN initiatives have focused on similar global actions and outcomes, including the Millennium Development Goals (MDGs, 2000–2015); the Sustainable Development Goals (SDGs, 2015–2030); and the High-Level Panel on Water (2015–2018) (Fig. 1). Many parallel local, regional (such as the Arab Water Forum) and global (for example, the World Water Forum and World Water Week) water-related forums have also emerged since 1977. Here we review the goals and progress up to the UN 2023 Water Conference in New York City and highlight three priorities for consideration and action.

Goals, then and now

Between 1977 and 2023, the world’s human population doubled to eight billion. Urbanization, agricultural expansion, industrial development, pollution and climate change have all placed enormous pressure on water resources. Since MDP, water has become scarcer per person and more polluted, and its availability in sufficient volumes and for essential uses (including ecosystem integrity) is threatened by climate change5,6. This increasing global water insecurity7,8 imposes high environmental and economic costs9,10,11,12 and magnifies risks13.

A crucial ongoing global goal has been to provide clean water and adequate sanitation services for all. Many other water goals that began at MDP have been retained and are part of multiple SDG targets (Fig. 2a). Some ongoing goals include access to improved sources of water and better sanitation services for all; better water data for improved decision-making; increased cooperation from the transboundary to the community level; reduced water pollution; and investment and innovation in water-related (primarily grey) infrastructure, which are included under SDG 6 (Clean Water and Sanitation) and SDG 11 (Housing). Other water-related issues, such as gender (highlighted at the International Conference on Water and the Environment in Dublin in 1992), agricultural water use, conflict zones and desertification (highlighted at MDP) have, respectively, been subsumed into SDG 5 (Gender Equality), SDG 2 (Zero Hunger), SDG 16 (Peace, Justice, and Strong Institutions) and SDG 15 (Desertification).

Fig. 2: Mapping the Goals from the First to the Second UN Water Conference.
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a, Goals from Mar del Plata are brown and map to the Report of the World Summit on Sustainable Development (1992), Dublin Statement and Report of the Conference (1992), High-level Panel on Water Outcome Document (2018), the Sustainable Development Goal 6 Synthesis Report on Water and Sanitation (2018) and the United Nations 2023 Water Conference Global Online Stakeholder Consultation for the Proposed Themes of the Interactive Dialogues (Summary report (2022)). Goals from World Summit on Sustainable Development (1992) are eucalyptus green and map to High-level Panel on Water Outcome Document (2018) and the Sustainable Development Goal 6 Synthesis Report on Water and Sanitation (2018). Goals from Dublin Statement and Report of the Conference (1992) are a beige-green and map to High-level Panel on Water Outcome Document (2018) and the Sustainable Development Goal 6 Synthesis Report on Water and Sanitation (2018). Goals from the Sustainable Development Goal 6 Synthesis Report on Water and Sanitation (2018) are blue and map to United Nations 2023 Water Conference Global Online Stakeholder Consultation for the Proposed Themes of the Interactive Dialogues (Summary report (2022)). b, Colours used for mapping goals in a do not accord with colours used for word clouds.

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In 1997, the UN member states adopted the Watercourses Convention. The convention highlighted the need to share water equitably and optimally between riparian nations to counter the prevalent notions of absolute territorial sovereignty and absolute integrity of state territory. It is worth noting that the Watercourses Convention did not include the human right to water. The international human right to water and sanitation was recognized in 2002 by the UN Committee on Economic, Cultural and Social Rights (General Comment No. 15)101 and, in 2010, in Resolution A/RES/64/292, the UN General Assembly declared water and sanitation as a human right100. These recognitions have not yet been sufficient to ensure clean water for all at an affordable price, including the impoverished, marginalized, many Indigenous peoples15 and those in remote locations in high and low-income countries16,17.

Colonization legacies within law and practices have left many low-income countries with water ‘ownership’ patterns tied to land ownership18 that impede water access and sharing. For example, while the South African Constitution acknowledges customary law, this law is not mentioned in the National Water Act (1998). Thus, customary water rights are frequently overlooked, and apartheid-era water rights continue under the Existing Lawful Use water entitlements19. Regulatory patterns in former colonial states have also promoted a preference for ‘full permanent sovereignty’ over natural resources, thus reinforcing competing interests between countries19.

Since MDP, water priorities have broadened from a focus on finance and grey infrastructure for water access to a greater emphasis on the environment20, especially climate change (Fig. 2b). Other vital priorities include: responding to sovereignty and water sharing between nations; the water–energy–food nexus8; water governance challenges from the local to the global21; freshwater ecosystem losses22,23; the conservation of green infrastructure24; gender and social dimensions of water25; private sector provision of water services; water pricing26,27; adaptation28; civil society’s participation in decision-making processes29 and the multiple values of water30.

Progress

Progress in the delivery of global water goals is mixed. For example, Water, Sanitation and Hygiene (WASH) was targeted in MDP (1977) as ‘Provision of drinking water and sanitation for all in 1990’, in MDG Target 7.C (2000) as ‘Reduce by half the proportion of people who were not able to reach or afford safe drinking water compared to 1990’ and ‘Halve by 2015 the proportion of people without access to improved sources of drinking water and improved sources of sanitation’, in the World Summit on Sustainable Development (2002) as ‘To halve by 2015 the proportion of people without access to basic sanitation compared to 1990’ and in SDG 6 (2015) as ‘Ensure availability and sustainable management of water and sanitation for all by 2030’. These WASH goals have either not been achieved or are contested31. Failure to meet global water goals goes beyond WASH, and progress towards them is detailed below.

Water supply and sanitation

In 2020, some 5.8 billion people had access to safely managed drinking water services—about 70% of the world’s population, which is a 2 billion increase since 200032. However, fewer than 30% of Africans have access to safely managed drinking water services compared with more than 90% of North Americans and Europeans (Table 1). At the current rate of progress (Fig. 3), many regions in either high or low-income countries will not achieve SDG Target 6.1: ‘By 2030, achieve universal and equitable access to safe and affordable drinking water for all’32.

Table 1 Access to safely managed water supply and sanitation
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Fig. 3: Worldwide progress towards access to safely managed drinking water and sanitation.
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The figure shows the difference in values between a weighted average calculation (continuous line) vs reported (dashed lines) values for water access (blue) and sanitation (orange). For access to improved water supply, there are about 81 countries (more than 4 billion population) where data is not reported. For access to sanitation, there is no data on the 81 countries (with a total population of .49 billion) where data is not reported. Data from the WHO/UNICEF Joint Monitoring Programme (https://washdata.org/data).

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About 60% of the world’s population in 2020 had access to safely managed sanitation services. However, approximately 1.7 billion people still lack basic sanitation services, and at least half a billion people are forced to defecate in the open. Furthermore, within countries access is inequitable, with rural regions having 26% lower coverage than urban regions32,33. At the current rate of progress (Fig. 3), the world will not achieve SDG Target 6.233: ‘By 2030, achieve access to adequate and equitable sanitation and hygiene for all and end open defecation, paying special attention to the needs of women and girls and those in vulnerable situations’.

Water quality

Water quality contributes to water scarcity and is a critical concern for water security34, given that water pollution arises from multiple anthropogenic and natural sources35,36.

Global water quality data are limited, particularly in Africa and parts of Asia and Latin America34. It is therefore difficult to determine on a global scale what progress has been made towards SDG Target 6.3 (ref. 98): ‘By 2030, improve water quality by reducing pollution, eliminating dumping and minimising release of hazardous chemicals and materials, halving the proportion of untreated wastewater and substantially increasing recycling and safe reuse globally’. Notwithstanding data limitations, the UN Environment Programme concludes that surface water quality has declined due to pollution in many of the rivers of Latin America, Africa and Asia34.

There have been notable improvements in water quality in some regions, especially in high-income counties and, most recently, in China37. The water quality of the River Rhine improved substantially between 1945 and 200838 and had ‘more or less’ stable water quality from 2008–202039. Despite this progress, some freshwater ecosystems in the European Union continue to degrade with pollution from chemicals and nutrients, exacerbated by water withdrawals40.

The River Ganges (Ganga) supports more than 600 million people and many bio-diverse ecosystems, yet it is one of the world’s most polluted rivers. The Government of India’s Ganga Action Plan (GAP) highlights the challenge of effectively responding to water pollution at scale. The GAP was launched in 1986 and became the National Mission for Clean Ganga in 2016, currently supported with US$1 billion from the World Bank to build institutional capacity and undertake infrastructure investments41,42. However, there are multiple long-standing challenges to a clean Ganga43,44 that include implementation delays, irregular release of funds, confusion over the roles of different government institutions and irregular monitoring. Consequently, claims of improvement in Ganga’s water quality remain contested43,44.

Water-use efficiency

The High-Level Panel on Water highlighted the need for ‘efficient use of water through a national policy framework that creates incentives for water users, including irrigators, to not waste or pollute water and to promote its reuse’45. This idea is frequently applied to irrigated agriculture with the goal to increase irrigation efficiency45 (that is, the ratio of water consumed in beneficial plant growth to total water withdrawals). Irrigation efficiency has been prioritized because irrigation accounts for about 70% of blue water (for example, freshwater lakes, rivers and aquifers) withdrawals and more than 80% of blue water consumption46.

Increased irrigation efficiency has been promoted to increase crop yields and to respond to a more than doubling of global irrigated areas over the past 60 years47. Higher irrigation efficiency helps farmers to increase crop production. However, this increase is frequently associated with reduced water availability elsewhere48 because greater beneficial water consumption promotes a ‘rebound effect’ that increases irrigation water demand49 and reduces the return flow of water from farmers’ fields to streams, rivers and aquifers. Consequently, without additional actions such as limits on water consumption50, increasing water-use efficiency alone will not achieve SDG Target 6.4: ‘By 2030, substantially increase water-use efficiency across all sectors and ensure sustainable withdrawals and supply of freshwater to address water scarcity and substantially reduce the number of people suffering from water scarcity.’

Transboundary water treaties

Bilateral water treaties have existed since the twenty-fifth century BC; today, they number some 600. These treaties have been critical in shaping principles of water law at a global level, that is: absolute territorial sovereignty (countries have absolute rights to use the water flowing in their territory, empowering upstream states); and the absolute integrity of state territory (countries have the right to receive the same quality and quantity of flows through time, benefiting downstream states)1.

Amending existing water laws is critical to ensure sustainable governance of water. At the global scale, three water conventions relate to transboundary waters, although none adequately responds to the hydrological impacts of climate change. First, the Ramsar Agreement on Wetlands (1971) had 172 contracting parties and entered into force in 1975 with the intent to stem the loss and degradation of wetlands of international importance. Second, the UN Economic Commission for Europe 1992 Water Convention had 46 contracting parties and was later opened for ratification by non-members of the UN Economic Commission for Europe. Third, the 1997 Watercourses Convention had 37 contracting parties and entered into force in 20141.

The 1992 Water Convention is notable for its focus on water pollution, and its follow-up protocol responds to concerns over human health related to drinking water and sanitation. The 1997 Watercourses Convention is important because it shifted long-standing notions of national sovereignty towards ‘do no harm’ to other states and equitable water sharing based on specified criteria and weights agreed to by riparian countries51. While hundreds of treaties govern transboundary waters, many countries are reluctant to ratify the Watercourses Convention, which specifies the need for equitable sharing. Transboundary cooperation, as envisaged by the UN and UN Economic Commission for Europe Water Conventions, has only progressed to a limited extent and, consequently, is limited to specific water issues51. Thus, much remains to be accomplished to achieve SDG Target 6.5: ‘By 2030, implement integrated water resources management at all levels, including through transboundary co-operation as appropriate.’1.

Protect and restore water-related ecosystems

About 35% of the world’s wetlands were lost between 1970 and 2015. This loss negatively impacts ecosystems, biodiversity and human welfare (Convention on Wetlands 2021)99. While some regions, such as North America, have performed relatively well in reducing recent losses, others, such as Africa and Latin America, have not52. Nevertheless, more wetlands are currently characterized as in a fair or good ecological state than previously, and only 23% of all wetlands are reported as being in a poor state53. Furthermore, Ramsar wetlands of international importance are considered to be in better condition than wetlands in general52.

About 70% of the global wetland losses happened in the twentieth century, with the highest loss rates in inland and coastal wetlands areas occurring since 195054. The current estimated total area of wetlands is 15–16 million km2 and loss rates are 0.2% yr−1 (ref. 55). Much of this loss is associated with land-use change, but inappropriate water regulation (drainage, water withdrawals, salinization, river regulation, pollution) has also been a contributing factor.

An important contributor to the degradation of water-related ecosystems is reduced forest cover. Deforestation changes water availability, contributes to soil erosion, degrades water quality and increases flooding risks. Although forest cover has recently increased in some regions, such as North America and Northern Europe56, the global forested area continues to decline (Fig. 4). Another critical pressure on water ecosystems is global blue water withdrawals, which have almost doubled since MDP (1977)57,58.

Fig. 4: Global Water Withdrawals (109 m3 yr-1), and Global forest area (106 ha yr-1) and deforestation (106 ha).
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Global water withdrawals and forest land area are shown. The inset shows global forest area and deforestation. Declining forest area is linked to degradation of water-related ecosystems. Data from FAOSTAT (https://www.fao.org/faostat).

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In summary, SDG Target 6.6 (ref. 98) has not been achieved: ‘By 2020, protect and restore water-related ecosystems, including mountains, forests, wetlands, rivers, aquifers and lakes’. Nor will SDG Target 15.1 be realized without a change in business-as-usual: ‘[c]onservation, restoration and sustainable use of terrestrial and inland freshwater ecosystems and their services, in particular forests, wetlands, mountains and drylands…’.

Data gaps

Eight of the 11 water-related indicators for SDG 6 are regularly assessed by at least half of all countries. These indicators include access to safe and affordable drinking water, increased water-use efficiency, implementation of integrated water resources management, protection of water-related ecosystems and international cooperation and participation of local communities in improving water and sanitation management. However, three indicators—access to sanitation, discharge of safely treated domestic and industrial wastewater, and bodies of water with good ambient water quality—are not regularly provided by most countries10. Furthermore, only 115 countries report data on total water access, and some (for example, Australia and China) only report urban water access, not rural water access (Fig. 5).

Fig. 5: Global data gaps on access to safe drinking water.
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Data provided by countries on access to a safely managed water supply are shown by category, where available. Data from the WHO/UNICEF Joint Monitoring Programme (https://washdata.org/data).

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Thus, despite substantial progress, data constraints identified at MDP, by the MDGs59 and highlighted in the High-Level Panel on Water (2018), remain an impediment to determining progress, identifying gaps, allocating funding and delivering action linked to human development60. Nevertheless, we contend that there are sufficient data to define priorities and act.

Priorities

Progress since MDP shows that there is no single approach to achieve sustainable and equitable goals of water for all. This is because the burdens of water insecurity are primarily realized at a local level (for example, droughts, floods, pollution, access and affordability, the distribution of property rights to water in society), yet the drivers range from local to global (for example, trade in virtual water, climate change, income and wealth inequalities, power imbalances within and across countries, failure to internalize costs and historical injustice and more)61. The delivery on global water goals has become more challenging since 1977. In addition to responding to injustice in the global North16 and global South62, decision-makers in 2023 are now constrained by planetary limits63 and tipping points64. Among the many priorities, here we highlight three for consideration at the second UN Water Conference: improved WASH42, investments in infrastructure (grey, green and soft), and a shift in values, behaviours and incentives.

Towards safe drinking water and sanitation

Realizing any of the SDG goals ranging from health to gender equality requires transformational change in access to safe water supply and sanitation for all32. A specific example in urban WASH services is Cambodia’s Phnom Penh Water Supply Authority, which began reforms in 1993 that subsequently resulted in a tenfold increase in its water distribution network. This change was accomplished by a ‘Swiss cheese model’ of cumulative actions to ensure WASH access65, rather than any single action. These actions included: inspired leadership and institutional reform; a good understanding of water customers; a focus on reduced water losses; removal of illegal connections; metering of all connections; a billing system that ensures all who receive water pay for it; and donor-financed infrastructure upgrades66.

Similarly, for potable purposes we highlight innovations in Windhoek (Namibia), a pioneer in directly providing reclaimed water67. For other locations such as Singapore, Orange County (USA), Wulpen (Belgium), Essex (United Kingdom) and Perth (Australia), reclaimed and/or recycled water is an essential part of water supply66. While much can be learnt from these examples, these places remain exceptions. For many urban residents, bespoke water reforms are required to overcome shortfalls. In cities like Jakarta (Indonesia)68, New Delhi (India)69 and Flint (Michigan, United States)70, unsafe tap water and incomplete sanitation and wastewater treatment services are a norm for those who cannot afford to pay for safe water access.

In contrast to urban experiences, enabling water and sanitation in rural areas is more difficult due to scale, demand and dispersed infrastructure, institutions (formal and informal) and finance14. Rural water supply experiences from African and Asian countries suggest a need to go beyond single source supply and ‘think beyond pipes’ to encompass diversified sources, ranging from private water vendors to rainfall. Enhancing access to safe water in rural areas is also linked to strengthening cultural water values and to the conservation of blue water sources (for example, springs, lakes and wetlands)14,32.

Investing in the three infrastructures

Much of the focus on delivering water infrastructure since MDP has been on grey infrastructure (for example, pipes, channels, treatment, buildings). Although grey infrastructure is needed in high, middle and low-income countries, we argue that green (for example, floodplains, wetlands, river channels, lakes and estuaries, soil, aquifers) and soft infrastructure (for example, governance, regulation, education, incentives and communication) are equally important priorities.

Grey infrastructure for WASH

Annual global subsidies of approximately US$320 billion are provided for delivering WASH services. Much of this expenditure goes to existing water services. Thus, the poorest with the least (or no) access to a centralized water system receive minimal support. Around 56% of subsidies go to the highest quintile households by income, and 6% go to the lowest quintile households71. Multiple informal markets and decentralized systems of water provision are frequently ignored within regulated and centralized pricing and infrastructure planning processes32.

By 2030, approximately US$1.5 trillion yr−1 of capital investments are required for grey infrastructure, with the most needed in low-income countries30. Hutton and Varughese72 estimated that the total annual capital costs to achieve SDG targets 6.1 and 6.2 range from US$74 billion to US$166 billion, comprising US$37.6 billion for safe water, US$19.5 billion for basic sanitation and US$49 billion for safe faecal waste management.

Sufficient investments to deliver SDG 6 will need multiple forms of financing, yet global private sector investments in greywater infrastructure in 2020 totalled only US$ 17 billion73. To overcome this challenge, the OECD recommends several financing pathways: improved soft infrastructure around the delivery of WASH services, such as an enabling environment (for example, decrease in non-revenue water); strategic investment planning; mobilizing additional investment by governments; restructuring risks and returns; and public–private partnerships leveraged by larger public investments73.

Green infrastructure for WASH and more

Green infrastructure has long been practised in the water sector, especially in conserving water catchments. For decades, cities such as Tokyo and New York74 have invested in protecting their watersheds to maintain high-quality water supply sources75. The financial pay-off has been a reduction in treatment, operation and maintenance costs23. A review of 309 large cities showed how degraded catchments increased operations and maintenance costs by 53 ± 5%, and replacement capital costs by 44 ± 14% (ref. 76). These benefits are not just measured in dollars; examples from Kenya show that conserving green infrastructure, such as natural springs, can reduce child mortality by one-quarter14.

Green infrastructure is increasingly acknowledged for its importance in delivering important ecosystem services (for example, freshwater provision, sediment regulation, flood mitigation and hydropower production)77,78. In addition, such infrastructure also supports cultural, recreational and amenity values while enabling flood management, groundwater recharge and more79. Nature-based investments in rain gardens, green roofs and urban constructed wetlands can also offset some of the negative impacts of grey infrastructure77,80. The benefits of maintaining and conserving green infrastructure are estimated to be worth US$3 trillion by 2050 in avoided replacement costs for grey infrastructure61.

Soft infrastructure for collective action

As synthesized by the World Bank42 and highlighted by the OECD73, soft infrastructure reform is critical to progressing towards SDG 6 and other SDG targets. According to the Water Policy Group, and others42,81, three important failures that need to be overcome are fragmented water institutions, inadequate and inaccessible data and information, and conflicts between water user groups. In response to these challenges, the World Bank has proposed a policy, institutions and regulations framework that connects data to WASH performance, reviews existing laws and the incentives they provide, builds institutional capacity and establishes effective planning to respond to stresses and shocks42. The lessons from this framework are applicable beyond WASH but can be difficult to implement because of regulatory capture, rent seeking and corruption82.

Regulatory capture83 occurs when state actors are ‘captured’ through a process of mediated corruption84. Such capture is not necessarily illegal and is facilitated by political donations, lobbying, ‘tit for tat’ favours and ‘revolving doors’ for decision-makers. This may be exacerbated by rigid decision hierarchies85, but Singapore is an example where top-down corruption control has been highly effective. Singapore’s approach has been supported by laws (Prevention of Corruption Act and Corruption, Drug Trafficking and Other Serious Crimes (Confiscation of Benefits) Act), an independent judiciary, strict and timely enforcement through the Corrupt Practice Investigation Bureau under the Prime Minister’s Office and a strict code of conduct for public servants with severe penalties for infringements.

Regulatory capture and rent seeking influence how money is spent and how decisions are prioritized82; it should be noted that corruption is widespread86 in some water sectors in high and low-income countries82. Responding to corruption requires bottom-up citizen vigilance plus international and national civil society support82. Anti-corruption measures must be fit for purpose. Nevertheless, we highlight some priorities: promoting decision-making at the scale where it is most effective and least vulnerable to manipulation; meaningful deliberations with all relevant stakeholders; transparency in process and decisions; and independent regulatory oversight.

Values, behaviours and incentives

Water has multiple use values (for example, WASH, agriculture, industry, ecological flows and so on) observable from people’s behaviours, and non-use or passive values (for example, aesthetic, spiritual and bequest), which are not often valued30. Measurement of these multiple values is essential because without estimates of non-market values (for example, water in rivers and lakes left in situ) and cultural values of water, decision-makers will, typically, only consider and/or prioritize market values (for example, water used to produce commercial crops)30.

Failure to fully value water in all uses, including in situ uses, has contributed to the degradation of green infrastructure that is critically important to deliver SDG 6, among other goals. Not, or only partially, valuing water87, and not accounting for the external costs imposed on others from water use (such as increased salinity, reduced stream flows from irrigation, or water-related health problems) contributes to water misallocation. That is, too much water is allocated for purposes that generate market values (for example, cotton production), and too little water is allocated for non-market needs (such as maintaining ecosystem services). This problem is most transparent within formal water markets (for example, in Australia, Chile, China, Spain and the United States), which have been effective, when there is adequate monitoring and compliance, at reallocating water on the basis of the marginal willingness to pay among competing water users.

Nevertheless, if the overall cap on water withdrawals in water markets fails to adequately consider non-market values, total water withdrawals are economically inefficient88. Failure to ensure an appropriate initial allocation of water rights, especially for Indigenous custodians of land89, and to prioritize drinking water needs for communities located on or nearby rivers where water rights are traded, undermines the social licence of water markets and increases inequities90.

Water regulators influence water conservation behaviours in multiple ways. For example, rationing constrains water availability or type of use and modifies household water conservation behaviours by requiring users to use less water. An alternative approach is to price non-essential water uses for household water supply and services and to provide a free allocation for essential uses and subsidies for low-income water users. Higher volumetric prices for households who can afford it can provide an incentive, but not an obligation, to conserve water91,92 where water use is metered. More equitable water outcomes can be supported by ensuring that additional revenues from higher water prices are directed to water suppliers to improve services and/or to reduce the fixed charges of poorer households. Non-market values and future water scarcity may also be included in regulated water prices. For example, in Australia, a water abstraction charge in Canberra93 proxies the external costs of household water consumption on downstream water users and in Sydney the volumetric price increases by 35% when water storage falls below 60%.

In many cities in middle and low-income countries there is inadequate household coverage of centralized water services, and this is frequently accompanied by supply interruptions94. Consequently, a proportion of urban households, as much as 50% in some cities, either supplement or completely obtain water independently (for example, wells, rivers) and/or through private water vendors. Although the volumetric price from water vendors can be much greater than centralized water systems95,96, they do offer a valuable service in cities as diverse as Dhaka, Bangladesh97, and Dar es Salaam, Tanzania96.

Conclusions

Progress in achieving the goals at MDP, the MDGs and the SDGs is mixed. Substantial progress has been made on WASH, important transboundary agreements and conventions have come into force (for example, the Ramsar, Watercourses Convention) and some measures of water quality have improved, mostly in high-income countries, since MDP. Nevertheless, none of the SDG 6 targets will be delivered by 2030, increases in water-use efficiency (SDG Target 6.4) alone will not ensure either sustainable water withdrawals or reduce the number of people suffering from water scarcity, and key data gaps remain.

Decades-long trends of reductions in the global area of wetlands and forests, coupled with ever-increasing global blue water withdrawals, pose increasing risks for human welfare and planetary health. A failure to achieve the key goals of the first UN Water Conference after almost five decades, and an increasing risk the world will cross a critical tipping point, together demand transformational change. For the second UN Water Conference, and beyond, we highlight the importance of three priorities: improved WASH; much greater and better-prioritized investments in grey, green and soft infrastructure; and a shift in values, behaviours and incentives. Without these and other changes that are specific to the biophysical and socio-economic contexts where they are applied, we will fail to deliver water for all.