Ageing Water Systems Face a Hidden Threat: An Ageing Population

Across the industrialised world, the pipes, dams, treatment plants and levees that deliver clean water and carry away wastewater are growing old at precisely the moment the societies they serve are growing old too. That uncomfortable coincidence is the starting point for a new Comment published in Nature Water, in which a multidisciplinary team of engineers, sociologists and public health researchers argues that the water sector can no longer treat infrastructure renewal and demographic change as separate problems. The authors, led by Farshid Vahedifard of Tufts University and including researchers from the United Nations University Institute for Water, Environment and Health, the University of California, Irvine, Mississippi State University and Utah State University, introduce a conceptual framework they call the infrastructure–society ageing gap, or ISAG, designed to force demographic ageing into every stage of water infrastructure decision-making.

The core observation is deceptively simple. Much of the water infrastructure in the United States, Europe and Japan was built during the mid-twentieth century, with design lives of fifty to a hundred years now expiring in large waves. The American Society of Civil Engineers’ most recent report card gives the sector grades that reflect chronic underinvestment, while the United Nations University has flagged ageing water storage infrastructure as an emerging global risk. Meanwhile, the United Nations Department of Economic and Social Affairs projects that the share of the world’s population over 65 will continue to climb steeply through mid-century, with the fastest growth in exactly the high-income countries whose networks are oldest. Two ageing curves, one physical and one human, are converging, and the authors contend that engineering asset management alone cannot capture what that convergence means.

The ISAG framework defines the gap as the mismatch between the ageing trajectory of water systems and the evolving needs, capacities and vulnerabilities of the populations those systems serve. The team identifies four interconnected pathways through which the gap emerges. The first concerns escalating demand for reliability: older residents, people with chronic illness and those with limited mobility are far more vulnerable to service interruptions, boil-water advisories and pressure losses. A single-day outage that is an inconvenience to a young, healthy household can become a medical emergency for a dialysis patient or an elderly person living alone. When the customer base ages, the same infrastructure failure produces disproportionately worse human outcomes.

The second pathway runs through the workforce. Water utilities face a well-documented retirement wave among operators, engineers and skilled tradespeople, which compounds the physical ageing of the assets themselves. The tacit knowledge needed to keep a fifty-year-old pumping station running often lives in the heads of workers approaching retirement themselves, and shrinking labour pools in shrinking regions make recruitment harder. The third pathway involves fiscal capacity. Communities with ageing populations often have contracting tax bases and rising social spending commitments, leaving less room for the capital investment that renewal demands. In Japan, where the Ministry of Land, Infrastructure, Transport and Tourism has documented widespread consolidation of small water utilities, the arithmetic of many elderly ratepayers supporting vast buried asset stocks has already become unsustainable for hundreds of small systems.

The fourth pathway is institutional and social: ageing populations can be less able to engage in the public processes, emergency preparations and adaptation planning that resilient water governance requires, and older neighbourhoods are often the ones served by the oldest mains and service lines. The authors organise these four pathways into what they describe as an infrastructure–society ageing decline spiral, in which deteriorating service quality drives out younger and more mobile residents, eroding the fiscal and workforce base still further and accelerating deterioration. Once that spiral takes hold, they argue, conventional repair cycles cannot keep pace, and the gap widens year after year.

To quantify the scale of the problem, the team draws on a broad body of official data: the American Society of Civil Engineers’ infrastructure assessments, Water UK’s economic analysis of asset maintenance and replacement, the Japanese ministry’s reform reviews, the US Army Corps of Engineers’ national levee database, the International Commission on Large Dams’ world register, OECD infrastructure investment outlooks, US Census Bureau demographic estimates and the UN’s world population prospects. A global dataset compiled by Zhang and Gu, published in Scientific Data, provides country-level indicators of infrastructure age. None of these sources alone links demography to infrastructure condition; that synthesis is precisely what the ISAG framework is meant to supply.

The proposal’s practical punchline is a pair of contrasting planning approaches. The first is demographic-blind investment, the status quo in most jurisdictions, in which renewal schedules are set purely by asset condition and risk scoring without reference to who lives downstream, downstream of the pipe, or behind the levee. The second is demographic-aware planning, in which intervention priorities, design standards and resilience investments are adjusted according to the age structure and projected demographic trajectory of the served population. Under the demographic-aware approach, an ageing service area would pull forward replacement of assets whose failure carries high public health consequences, justify higher redundancy in distribution networks serving vulnerable populations, and tilt investment toward measures such as backup power, pressure management and rapid response capacity.

The authors are careful to say the framework is a decision-support concept rather than a formula. Its value, they suggest, lies in making an invisible coupling visible: utilities that benchmark their asset age against demographic projections, and integrate social vulnerability data into risk models, will make different and better-targeted choices than those that do not. The framework spans the full infrastructure life cycle, from planning and design through operation, maintenance, rehabilitation and eventual decommissioning, and the authors argue that demographic ageing should be treated as a first-order design parameter on the same footing as hydrology, hydraulics and structural condition. That represents a significant cultural shift for a profession whose textbooks have historically treated the human population as a static demand number rather than a dynamic, ageing system in its own right.

The timing of the Comment is deliberate. It forms part of a series contributing to the 2026 UN Water Conference, supported by UNU-INWEH as part of the UN-Water initiative to ground water policymaking in evidence. With governments preparing national water security strategies and capital programmes running into the hundreds of billions of dollars, the authors hope the ISAG framing will find its way into regulatory guidance, utility asset management plans and international lending criteria. The stakes, they note, are not merely economic. A water system that fails its most vulnerable users fails everyone’s trust in it, and rebuilding that trust after crises is far more expensive than preventing them. The authors declare no competing interests, and correspondence for the work is handled through Tufts University’s Department of Civil and Environmental Engineering.

What the paper ultimately offers is a reframing: the water crisis of ageing infrastructure is also, unavoidably, a social and demographic crisis. Pipes and people are growing old together, and the institutions responsible for water must learn to plan for both at once. If the authors are right, the utilities, ministries and municipalities that internalise this coupling earliest will be the ones that keep taps running safely for the populations that depend on them most.

Subject of Research: A framework for integrating demographic ageing into water infrastructure planning

Article Title: To fix ageing water infrastructure, we must plan for an ageing population

Article References: Vahedifard, F., Azhar, M., Li, J., AghaKouchak, A., Brown, D. C., Marfeo, E., Null, S. E., Spearing, L. A., & Tajik, N. (2026). To fix ageing water infrastructure, we must plan for an ageing population. Nature Water, 4(9), 1062-1067. https://doi.org/10.1038/s44221-026-00711-z

Image Credits: AI Generated

DOI: 10.1038/s44221-026-00711-z

Keywords: ageing water infrastructure, infrastructure-society ageing gap, demographic ageing, water utilities, water governance, asset management, Nature Water, resilience planning, public health, UN Water Conference, vulnerable populations, infrastructure life cycle