Regions around the world are increasingly experiencing water stress and scarcity, threatening economic development, food security, and environmental sustainability. Already today, almost two-thirds of the world’s population experiences severe water scarcity for at least one month each year, and climate change is expected to make water flows more irregular.
Water scarcity is generally referred to when the ratio of water withdrawals to the long-term average available water resources for a given territory and period exceeds 20%, indicating unsustainable use of freshwater resources. In 2019, almost a third (29%) of the European Union (EU) territory experienced water scarcity conditions in at least one quarter of the year, with a regional concentration in southern Europe.
However, the effects of the climate crisis can only partly explain the troubling trends in water scarcity in many parts of the world that we have been observing. In fact, they are aggravating existing water stress conditions substantially caused by overabstraction of groundwater and surface water depending on the type of human activities and population size. In addition, landscape and geological characteristics of basins determine water availability. 2023 has also seen the return of the El Niño phenomenon, a naturally occurring climate pattern that increases the risk of extreme weather events in several parts of the world including extended droughts and heatwaves.
A recent example from Montevideo, Uruguay shows how a severe drought, combined with aging infrastructure and mismanagement of major reservoirs can lead to severe water scarcity. To stretch water supplies, the public water utility has been mixing salty water from the Río de la Plata estuary with fresh reservoir water, resulting in tap water considered as no longer drinkable according to sanitary criteria.
Need to strengthening infrastructures and embracing new water sources
The situation in Montevideo (Uruguay) can become a lesson for cities around the world and stresses how water scarcity is directly linked to the acceleration and spreading of freshwater pollution. It also illustrates the risk of not adapting infrastructure to challenges such as population growth and more frequent and intense extreme weather events. Apart from large investments needed to modernize water infrastructure in order to make water use more efficient, we also need to consider alternative water supplies. Reusing water from urban wastewater treatment plants is one of them. Reused wastewater can ensure a safe and predictable source of water when appropriately treated, whilst lowering the pressure on water bodies and enhancing the ability to adapt to climate change. In the EU, for example, a new Regulation on minimum requirements for water reuse for agricultural irrigation applies since June 2023. The Regulation aims to harmonize minimum quality requirements for reused water in agriculture and monitoring requirements across the Member States. The Regulation can have significant impact as the agricultural sector is one of the largest water-using sectors. In 2017, together with forestry and fishing, it was responsible for 58% of all water abstractions in Europe. Increasing water efficiency in agriculture is another big challenge, that can be achieved through pressurized irrigation systems on fields or optimized irrigation schedules in greenhouses, using Artificial Intelligence, among others.
But also outside of the agricultural sector, urgent steps need to be taken to recycle and conserve dwindling water resources. In the EU, the energy sector is the second-biggest water user due to water-intensive cooling of thermal plants powered by fossil fuels. With the increased use of renewable energy produced through solar PV and wind, the water footprint of the energy sector is expected to decrease. How big this reduction will be, will, however, also depend on the future energy mix, as low-carbon technologies like “green” hydrogen are highly water-intensive.
A widely-discussed technique to reduce pressure on freshwater and groundwater is desalination, a method that is already supplying more than 300 million people worldwide with water. Despite major technical advances over the last decades, desalination is, still highly energy- and cost-intensive, limiting its application mostly to wealthy economies in the Middle East, as well as the US and Australia. In addition, there are environmental concerns about the byproduct of this technique: hypersaline concentration, or waste brine, that if pumped back into the ocean can harm local marine ecosystems. Currently, desalination can be only one of many measures to address water scarcity, and its advantages and disadvantages must be carefully weighed against those of water recycling and conservation.
Nature-Based Solutions for Water Scarcity
Cost-effective solutions to water scarcity can be found by harnessing the services that ecosystems around us provide. So called Nature-based Solutions are inspired and supported by nature. Examples range from large-scale river restoration projects to greening roofs or walls in densely populated areas. Especially in cities and their surroundings, where the pressure on water resources is particularly high, Nature-based Solutions can serve multiple functions and can be implemented on a small scale at low cost. Apart from restoring degraded ecosystems and alleviating water scarcity and flood risks, they can have positive effects on human health and well-being, social cohesion as well as the population’s resilience. Many Nature-based Solutions address water scarcity by improving water retention, e.g. through the restoration of rivers with plant buffer strips or the creation of water retention ponds that can store rainwater. The new European Nature Restoration Law – that passed through the EU Parliament on July 12 after controversial discussions – provides a suitable framework to scale up ecosystem restoration in Europe.
A related concept that has gained momentum in recent years is the Sponge City concept, that builds on the idea to capture as much rainwater as possible through natural infiltration into groundwater. To do so, the concept aims at reducing sealing in cities that prevents water from infiltrating into the ground while at the same time creating a network of decentralized water storage. Reduced sealing can result in lower flood risk while the captured rainwater can be used for human consumption and support water-dependent ecosystems. In addition, the retained water can reduce the heat island effect in summer, as evaporating water cools down overheated densely built neighborhoods and nourishes plants that provide shade. The power of this approach lies in taking into account the dynamics of water extreme events, in which heavy rain events and droughts increasingly occur alternately. In addition, the Sponge City approach allows to address several Sustainable Development Goals (SDGs) by making cities more inclusive, safe, resilient and sustainable (SDG 11) and contributing to clean water and sanitation (SDG 6). By contributing to climate adaptation, disaster risk reduction and sustainable urban development, the approach depicts a promising sustainable adaptation pathway much needed to make cities more resilient.
Implementing the Sponge City concept requires a paradigm shift in municipalities which often operate in silos and lack horizontal coordination, hindering water-sensitive planning across sectors. Setting up dedicated institutions can help steering this process. In 2018, the City of Berlin, Germany, for example, created the Rainwater Agency, an organization responsible for driving the large-scale implementation of the Sponge City concept in the city. At the same time, the Agency advises private entities in implementing water retention measures. This transformation is estimated to cost the City of Berlin up to € 10 billion, which underlines that also Nature-based Solutions require substantial investments if implemented systemically and at large-scale. Overall, UNEP estimates the current funding gap for Nature-based Solutions to the interlinked climate, biodiversity and land degradation crises to be more than US$ 200 billion per year. It urges to quickly ramp up investments into nature to US$ 384 billion per year by 2025, more than double of the current amount.
Adaptive Governance to Alleviate Water Scarcity
Inefficient water management structures and incapacities to govern water resources in a sustainable way are a common thread observable all around the world. While some major cities around the world have positioned themselves as forerunners in implementing innovative nature-based as well as “grey” or technical solutions, high implementation costs and lacking personal resources pose challenges particularly for small and medium-sized cities as well as rural areas. Their administrations often lack the resources and tools to address the underlying root causes of water scarcity. Strengthening capacities on climate change adaptation in municipalities and regional governments and tackling water scarcity as a cross-sectoral challenge will be of key importance over the next years.
In the quest of solutions to water scarcity, one should not forget the crucial role of local communities in managing and using water. The involvement of local stakeholders in co-creation processes can also increase the buy-in and acceptance of measures against water scarcity, as illustrated in this report focusing on Nature-based Solutions. Living up to the leave no one behind principle, institutions and governance approaches at local level should take socio-cultural aspects of managing and consuming water into account. These aspects should also be considered when designing measures to decrease individual water consumption, e.g. through awareness-raising or incentivizing measures that motivate behavioral change. Assessments of vulnerability to water scarcity can help prioritize measures and tailor solutions based on needs of the most vulnerable parts of the population.
Harnessing the Potential of Digitalization
New opportunities open up through digital innovations in the water sector. These range from Artificial Intelligence-powered irrigation systems or sensors for predictive maintenance and flood control of wastewater systems to Augmented Reality tools making sustainability issues in water management tangible to the public. To date, water service providers are still lagging behind in adopting digital services, automation, and technological innovations that enable them to improve their operational and management obligations. Innovations are also hampered by a regulatory framework not prepared for the huge opportunities and challenges that come with digitalization in the water sector. With the appropriate regulatory framework, such digital solutions can be another piece of the big puzzle to alleviate water scarcity around the globe.