Did you know that more than 2 billion people lack access to safe drinking water and more than 4 billion lack access to proper sanitation1? The UN predicts that there will be a 40% gap between water demand and water supply by 2030. A rapidly growing population has increased environmental degradation, and climate change will increase the scarcity of water. There is a need for new solutions to manage water resources in order to meet rising challenges to water security and avoid aggravating negative impacts on the ecosystem.
Many solutions are emerging to tackle freshwater scarcity, including using natural ecosystems, technological developments in desalination and advanced environmental monitoring for water resource management.
In order to meet the UN SDGs, the world needs to invest between $237 - $664 billon on water supply, sanitation, flood protection and irrigation every year until 20302. As concluded in a new report from World Bank and WRI2: Ecosystem-based solutions can fill the water supply gap in a cost-effective way. Establishing and conserving forests or wetlands are examples of ecosystem-based measures that contribute to water management.
Forests improve water quality by trapping sediments and water pollutants, with the ability to provide clean water at costs lower than industrial water treatment plants. As an example, restoration of native forests in targeted locations in Rio de Janeiro have been estimated to save the local government $79 million compared to conventional water treatment systems3. Almost half of the world’s one hundred largest cities rely on protected forest areas as their source of drinking water. Wetlands, like forests, have a natural ability to filter effluents and absorb pollutants, but wetlands can also store large amounts of water, potentially limiting flood damage. It is also possible to construct synthetic wetlands that function as biological wastewater treatment systems to control nutrient pollution from discharged water. Water supply systems that are created to use or mimic natural processes and ecosystems are often referred to as nature-based solutions to water management4.
Nature-based solutions can be combined with conventional water infrastructure to increase sustainability and are often used in urban spaces to enhance both the quality of life and address water issues. By investing in such solutions, cities can act like sponges that soak up floodwater and release it when needed and as such also increase resilience to floods and draughts caused by climate change. One interesting example is the development of sponge cities in China, where permeable surfaces and green infrastructure is built out so that 80 % of urban areas in China will re-use at least 70 % their rain water5. There are different types of nature-based solutions for water, ranging from the micro/personal scale to landscape applications and solutions for urban settings (green walls, roof gardens, vegetated infiltration or drainage basins)6.
Developing natural solutions will be a key to sustainable management of water availability and quality, and an important complement to human-built, or ‘grey’ infrastructure. Water scenario analyses also show that nature-based solutions are more efficient than grey infrastructure in securing safe and predictable access to clean water in a global perspective7.Towards sustainable desalination
Desalination, the process by which seawater is converted to freshwater, will be important to narrow the water demand-supply gap8 by extending water supplies beyond what is available from the hydrological cycle. Desalination is currently concentrated in high-income developed countries. One example is Saudi Arabia, where 50 per cent of the country’s 34 million people drink desalinated water. Reverse osmosis is the most prominent desalination technology worldwide9. As desalination is the process of removing salt from water, a problematic byproduct is toxic hypersaline concentrate, brine, often polluted with copper. Research shows that there are emerging opportunities for sustainable handling of brine, including production of commercial salt, metal recovery, and fish farming10.
Earth observation information from satellite imagery and other data on global freshwater supply (surface water and ground water) will improve our understanding of freshwater capacity in different areas of the world8. In combination with historical data on water supply such as the Global Surface Water Explorer,11 these will be important decision-making tools for water managers and governmental agencies within freshwater management.
The demand for sustainable freshwater solutions will increase due to the growing need to close the supply-demand gap. Nature-based solutions have a high potential to meet contemporary and future water resources management challenges as reflected in the SDGs. Scenario analyses demonstrate that implementation of such solutions is a requirement for achieving social and economic development towards 2030. In addition to improving the supply of clean fresh water, such solutions provide a number of other benefits to the local environment, such as increased biodiversity and resistance to flood and drought.
Desalination can provide an unlimited, climate-independent and steady supply of high-quality water if solutions are developed for sustainable brine management. Growth patterns and economics indicate a promising market uptake of such technologies around the world10.Risks and uncertainties
The benefits of nature-based solutions are not generally known to the public, water resource managers, or policy makers, and this lack of information can be a barrier to efficient uptake of the technology. The management of water resources naturally involves many stakeholders, both upstream and downstream. With many stakeholders, potentially from different jurisdictions, it is challenging to coordinate and incentivize actions to develop forests, wetlands and marshes.
Another potential risk for the uptake of such technologies is the lack of technical guidance and tools to determine the right mix of nature-based solutions and grey-infrastructure options. It is also more difficult to estimate the value added from a wetland than it is to estimate the effect of a more narrow, conventional water management system. Nature-based solutions will not provide water in the same mechanical and measurable way as conventional water management systems.
High energy demand and brine production are key downsides of desalination. Disposal of toxic brine is both costly and has negative environmental impacts. For affordable and environmentally-friendly desalination systems to be rolled out in low-income and lower middle-income countries, clean energy must be available and innovative financial mechanisms must be in place.Contributors
Main author: Marte Rusten
Contributors: Anne Louise Koefoed; Bente Pretlove
Editor: Ellen Skarsgård
- CNN (2018) 'China's 'sponge cities' aim to re-use 70% of rainwater'
- UN Environment-DHI, UN Environment and IUCN 2018. Nature-Based Solutions for Water Management: A Primer
- Jones E., Qadir M., van Vliet M.T.H., Smakhtin V., Kang S-M. (2019). The state of desalination and brine production: A global outlook,Science of The Total Environment,Volume 657,2019