The world’s road to water scarcity: shortage and stress in the 20th century and pathways towards sustainability

TLDR

Water scarcity is a growing global concern, yet its historical development and drivers remain poorly understood. The study assesses continuous sub‑national trajectories of blue water consumption, freshwater availability, and water scarcity across the 20th century. Water scarcity is quantified by evaluating shortage—low per‑capita availability—and stress—high consumption relative to availability—across sub‑national units. Water consumption quadrupled in the 20th century, raising the number of people experiencing scarcity from 0.24 billion to 3.8 billion, with almost all sub‑national trajectories showing rising scarcity and new archetypes proposed to guide mitigation.

Abstract

Abstract Water scarcity is a rapidly growing concern around the globe, but little is known about how it has developed over time. This study provides a first assessment of continuous sub-national trajectories of blue water consumption, renewable freshwater availability, and water scarcity for the entire 20 th century. Water scarcity is analysed using the fundamental concepts of shortage (impacts due to low availability per capita) and stress (impacts due to high consumption relative to availability) which indicate difficulties in satisfying the needs of a population and overuse of resources respectively. While water consumption increased fourfold within the study period, the population under water scarcity increased from 0.24 billion (14% of global population) in the 1900s to 3.8 billion (58%) in the 2000s. Nearly all sub-national trajectories show an increasing trend in water scarcity. The concept of scarcity trajectory archetypes and shapes is introduced to characterize the historical development of water scarcity and suggest measures for alleviating water scarcity and increasing sustainability. Linking the scarcity trajectories to other datasets may help further deepen understanding of how trajectories relate to historical and future drivers, and hence help tackle these evolving challenges.