950 Recent climate variability has been marked by an accelerated emergence of extreme events linked to the El Niño–Southern Oscillation (ENSO), particularly the increasing persistence of multiyear La Niña episodes since the late twentieth century (see Fig. 1). This shift is associated with changes in the mean state of the tropical Pacific -notably the relative warming of the western Pacific compared to the central Pacific- which modifies key ocean–atmosphere feedbacks and favors prolonged La Niña conditions with heightened socioeconomic impacts (Wang et al., 2023). As a result, ENSO increasingly amplifies the occurrence and intensity of extreme hydrological events, exacerbating floods and droughts across regions (Islam, 2025). Figure 1. Sea surface temperature anomalies showing El Niño and single-year and multiyear La Niña occurrences Source: Wang et al., 2023. These impacts now unfold on a warmer background climate, as 2023–2025 were the three warmest years on record (see Fig. 2), further intensifying the severity of ENSO-related extremes (World Meteorological Organization [WMO], 2026; Copernicus Climate Change Service [C3S], 2026). Figure 2. Global annual surface air temperature anomaly relative to the pre-industrial period. The dashed line indicates the 1.5°C threshold; shaded area highlights 2023–2025. Source: Copernicus Climate Change Service (ERA5) data; authors’ elaboration. These dynamics are increasing water stress in regions with structural or seasonal scarcity and even in areas without a historical deficit of water resources. Moreover, these pressures are compounded by gaps in the very systems intended to manage them. In fact, in most countries currently experiencing, or projected to experience, water stress, weaknesses exist in water resources management. These weaknesses manifest in: i) water information, both for climate scenario modeling and for monitoring the quantity and quality of surface and groundwater resources, as well as its use for basin-level decision-making; ii) efficiency in water use, characterized by high losses and limited reuse; and iii) the timely development of conventional and nature-based water supply augmentation projects. Monitoring networks remain fragmented and uneven, with limited hydrometric and piezometric coverage often designed under assumptions of climatic stationarity, reducing their capacity to detect shifts in water availability (European Union, 2024). Continuous water-quality monitoring, QA/QC, and data interoperability are also inconsistent. Although advanced tools -including groundwater geophysics, AIassisted inversion, environmental isotopes, Earth observation, continuous sensing, and coupled modelling-
RkJQdWJsaXNoZXIy MTM0Mzk2