Fifty percent of people on the planet live in cities, and the urban population grows by two people every second. Ninety three percent of this urban growth is occurring in poor or developing countries, and nearly forty percent of the world's urban expansion is growing slums. Increasing urbanisation and economic growth provides significant benefits, but it also poses a range of challenges.
Increasing water abstractions in cities coupled with irregular water availability due to climate change and other pressures, means that cities are exploring alternative strategies for securing water supplies. This can mean diversifying water supply options from a single source to a portfolio of supplies such as surface water, groundwater, re-used water, desalinated water and harvested rainwater. Effective management approaches include cooperation between catchment authorities and end users, such as utilities and industries, to put in place strategies like water demand and exploring pricing options, which still maintain people’s human right to water and sanitation. For example, the Public Utilities Board (PUB) in Singapore has adopted demand management which combines strategies for consumer behaviour change, reducing unaccounted water losses to less than five percent, introducing a water conservation tax in addition to water pricing, and enforcing mandatory and voluntary measures for water conservation.
At the same time, cities are increasingly competing for water resources with other water users such as agriculture and energy. We often see these essential resources as separate entities, but they are inextricably linked. The Water-Energy-Food nexus explores how these three areas are interlinked, and how development in one area can affect the others. Energy is needed for water and wastewater treatment as well as distribution to consumers. Water needs to be stored for farmers to be used for irrigation of crops. Management of watersheds is important to sustain sufficient flows for hydropower production, as well as providing cooling water for thermal power plants.
To address such competing water needs for the water, energy and food nexus means exploring opportunities to optimize water infrastructure for multiple purposes to supply water to cities and industry. This infrastructure includes engineered structures such as dams, reservoirs, canals and irrigation systems. But it also includes ecosystems and watersheds that act as ‘natural infrastructure’: mangroves that buffer against severe storms, floodplains that absorb flood waters, forests that stabilize soils, lakes and wetlands that clean and store water. Well-functioning and healthy natural infrastructure supports the performance of engineered infrastructure. For example, the maintenance of catchment forest areas can prevent increases in sedimentation that can affect downstream reservoir capacity. This interaction requires cities and industries to engage effectively and efficiently in river basin management and support the equitable negotiation of water allocations across users.
There are more and more discussions about the water, energy and food nexus and how we should be linking these three areas. This perspective thinks about taking the ideas a step further on how to practically plan and implement infrastructure and technology that can link the three elements while minimizing trade-offs. For example, looking at providing different qualities of water for different uses. Victoria Falls applied this approach by encouraging the use of river water for watering gardens, hotel grounds and golf courses, thereby reducing the cost of energy and chemicals for treatment.
There is a rich array of experience and practical knowledge across professional fields including farming, energy-production, natural resource management, and engineering. The challenge is actively bringing these together to provide active learning and knowledge exchange. The International Water Association (IWA) and the International Union for Conservation of Nature (IUCN) are looking at how to make this happen through the Nexus Dialogue on Water Infrastructure Solutions, which provides a forum for sharing experiences, lessons, tools and guidelines on how portfolios of water infrastructure and technologies can address nexus challenges. To learn more and contribute visit the Water Nexus Solutions website.
Also check the 'nexus'-debate on the IWA Water Wiki
This blog is intended as an information document only. It does not represent the views of the IWA membership as a whole and does not constitute the formal policy of IWA.
Photo credit main picture: Wigwam Jones