It also means water supply will remain consistent, despite climate change impacts, such as a lack of rainfall and drought, or too much rain and being flood resilient. Sustainable water also means that the economics stack up in matching supply and demand and the water delivery process is as efficient as possible. Water sustainability, meanwhile, can also mean energy neutrality by coupling traditional water treatment technologies with renewable energies. 

Sustainable water means a nation that can be water self-sufficient: ensuring there is enough water to meet multiple needs, from agriculture to municipal and industrial. 

Sustainable water management means the ability to meet the water needs of the present without compromising the ability of future generations to do the same. Achieving sustainable water management requires a multidisciplinary and holistic approach in which technical, environmental, economic, landscape aesthetic, societal and cultural issues are addressed.

On a global scale, having sustainable water means to provide each person on the planet with affordable access to the minimum 20 to 50 litres of daily water required to sustain life. This follows the United Nations General Assembly recognition of “the right to safe and cleaning drinking water and sanitation as a human right that is essential for the full enjoyment of life and all human rights”.

Water sustainability also means effective and holistic management of water resources. There are now multiple demands on water resources, which drive the need for sustainable, integrated and holistic water management.

“A sustainable water cycle in which we are able to meet our needs for water and sewerage services while enabling future generations to meet their own needs.”

Surface water

Surface water is limited as is unequally distributed around the world and pollution from various activities means that surface water without treatment is not suitable for drinking. If properly constructed, dams can provide a sustainable water supply as the structures can be used for power generation, irrigation, flood prevention, water diversion and navigation. However, large-scale dam projects may present challenges to sustainability: negative environmental impacts on wildlife habitats, fish migration, water flow and quality and socioeconomic impacts. Therefore, a sustainability impact assessment should be performed.

Groundwater

Groundwater accounts for more than 50 per cent of global freshwater and is critical for potable water. Groundwater can be a sustainable supply of water only if the amount of water entering, leaving and being stored in the system is conserved. The IWA says unsustainable groundwater use results in water-level decline, reduce streamflow and low quality water, directly impacting local communities.

Desalination

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In some nations lacking freshwater, desalination has provided an adequate water supply for many years. However, higher energy demands from both thermal and membrane-based compared to groundwater and surface water treatment have challenged the adaption of desalination as a sustainable one. However, the IWA said that sustainability of desalination could be improved if it is coupled with renewable energy. Decentralised, solar power desalination has been recommended as a way to provide more sustainable water for Greece’s 6000 islands.

Reclaimed water

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Reclaimed water, or water reuse as it’s known, can also be a sustainable source for water supply and can alleviate stress on primary water resources, such as surface and groundwater. Depending on the given application, reclaimed water must be treated to provide an appropriate quality, for example for irrigation or industry use. The level of water reuse varies globally. Countries such as Spain and China continue to lead the way in water reuse, with the later accounting for 49 percent of capacity contracted between 2010 and 2017.

Sustainable water resources management

Sustainable water supply is a component of integrated water resource management, according to the IWA. The association identifies it as the “practice of bringing together multiple stakeholders with various viewpoints to determine how water should best be managed”. To decide if a water system is sustainable, various economic, social and ecological considerations must be considered.

Meanwhile, the United Nations (UN) has outlined the following areas where sustainable water resources management will need to take place, which ties in with its overarching goal of “Securing Sustainable Water for All”.

Agriculture

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Agriculture is by far the thirstiest consumer of water globally, accounting for 70 per cent of water withdrawals worldwide, although this figure varies considerably across countries. Rainfed agriculture is the predominant agricultural production system around the world, and its current productivity is, on average, little more than half the potential obtainable under optimal agricultural management. By 2050, world agriculture will need to produce 60% more food globally, and 100 per cent more in developing countries.

Industry and energy

Together, industry and energy account for 20 per cent of water demand. More-developed countries have a much larger proportion of freshwater withdrawals for industry than less-developed countries, where agriculture dominates. Balancing the requirements of sustainability against the conventional view of industrial mass production creates several conundrums for industries. One of the biggest is globalisation and how to spread the benefits of industrialisation worldwide and without unsustainable impacts on water and other natural resources.

Domestic sector

Municipal water use accounts for 10 per cent of total water use. And yet, worldwide, an estimated 748 million people remain without access to an improved source of water, and 2.5 billion remain without access to improved sanitation.

Cities

^{Image credit: Chicago Council on Global Affairs} 

More than half the world already lives in urban areas, and by 2050, it is expected that more than two-thirds of the global population of nine billion will be living in cities. Furthermore, most of this growth will happen in developing countries, which have limited capacity to deal with this rapid change, and the growth will also lead to increase in the number of people living in slums, which often have very poor living conditions, including inadequate water and sanitation facilities. Therefore, the development of water resources for economic growth, social equity and environmental sustainability will be closely linked with the sustainable development of cities.

Ecosystems

Perhaps the most important challenge to sustainable development to have arisen in the last decades is the unfolding global ecological crisis that is becoming a barrier to further human development. From an ecological perspective, sustainable development efforts have not been successful. Global environmental degradation has reached a critical level with major ecosystems approaching thresholds that could trigger massive collapse. The growing understanding of global planetary boundaries, which must be respected to protect Earth’s life support systems, needs to be the very basis of the future sustainable development framework.