Impact Chains to investigate the complex 2022 drought dynamics in the upper Adige River Basin

Recent drought events in Europe have generated cascading impacts across interconnected sectors. Droughts in mountain regions are increasingly complex phenomena, as winter snowpack deficits compound with low rainfall and high temperature anomalies in spring and summer, reducing water availability from upstream to downstream and amplifying impacts across water-dependent systems. Unfolding this complexity into actionable risk diagnostics remains challenging, especially when impacts emerge from interacting hazards, affect multiple interconnected sectors, and evolve through lagged processes and feedbacks. Conceptual frameworks such as Impact Chain (IC) provide a structured representation of hazard–impact relationships, yet their application to compound drought events often remains limited in capturing temporal dynamics, feedback mechanisms, and event-specific processes.

The Upper Adige River Basin in the Italian Alps exemplifies these challenges, given its strong dependence on snow accumulation and melt and the coexistence of competing water uses. During the 2022 drought, the basin experienced widespread impacts across water-dependent sectors. Despite the severity of these impacts, existing assessments have provided limited insights into how compound climatic drivers and sectoral vulnerabilities interact to produce these outcomes.

This study applies and refines the IC framework to perform a forensic analysis of the 2022 drought impacts on the water sector in the Upper Adige River Basin. A scoping phase identified affected sectors and key impact pathways; a qualitative analysis developed a detailed water-sector IC capturing hazard, exposure, vulnerability, impact, and adaptation factors; and a quantitative characterization linked the IC to hydroclimatic variables (SWE, precipitation, temperature, evapotranspiration, and runoff) using threshold-based deficit detection and cross-correlation analysis to assess interactions and time-lagged dependencies.

During winter 2021–2022, snow water equivalent (SWE) remained persistently below average, reaching a seasonal maximum of approximately 105 mm compared to a long-term mean peak of about 150 mm typically observed in mid-March. Snowmelt occurred anomalously early, with SWE dropping below 30 mm by late May, nearly two months earlier than average, substantially reducing meltwater availability during the summer peak-demand period. Concurrently, air temperature exhibited sustained positive anomalies (approximately +1.5 to +3.5 °C from mid-May to mid-September), enhancing evapotranspiration, accelerating snowpack depletion, and contributing to prolonged low-flow conditions. These hydroclimatic anomalies translated into reduced hydropower production, irrigation water shortages affecting agriculture, increased forest fire activity, and heat-related stress on human health.

Overall, these findings advance the IC approach by demonstrating its usefulness as a forensic framework for disentangling how multiple interacting hydroclimatic conditions combined to produce the observed drought impacts. By integrating observational and model-based data into a previously qualitative framework, the approach supports a more structured interpretation of impact propagation across interconnected systems. The IC-based framework also shows potential for informing impact-based early warning systems for compound and multi-hazard hot–dry events, as well as for drought risk assessment and adaptation planning in snow-dependent, multi-sectoral alpine basins facing intensifying climate extremes.