The dual role of irrigation in the groundwater budget under baseline conditions versus the 2022 drought: Lessons for future climate adaptation

• Surface-water-fed irrigation can recharge groundwater systems. • Groundwater-fed irrigation depletes groundwater. • 2022 drought determined significant changes in groundwater budget. • Surface-water-fed areas suffered a severe lack of recharge in 2022. • Groundwater-fed areas depletion increased by up to 100% more during 2022 summer. Groundwater is facing shortage scenarios worldwide due to a changing climate, but systems governed by different recharge processes may react differently. Hence, understanding groundwater budget components is critical for sustainable resource management. This study analyzes seasonal groundwater level patterns from ca. 60 wells, investigating different hydrogeological contexts and water management practices. In the first phase, data under baseline conditions (2013–2021) are analyzed to identify the average seasonal patterns and the associated recharge and discharge processes. Successively, the 2022 data is compared with baseline data to quantify the effect of the hydrological drought. Results show that in surface-water-fed irrigation areas, the absence of surface water during the 2022 summer, related to winter snow scarcity in the Alps, caused significant disruption of the typical groundwater seasonal profile. The winter groundwater table decrease was more than twice the average decrease under baseline conditions, and the summer rise was the 30% of the average rise under baseline conditions. This is related to the missing recharge and the increased abstraction of groundwater to fill the lack of surface water for irrigation needs. Therefore, in a scenario of dryer summers linked to climate change, the plausible transition toward more efficient irrigation methods or groundwater irrigation could cause severe groundwater depletion and compensation measures will be needed. Conversely, in groundwater-fed irrigation areas, the increased irrigation needs during the 2022 summer determined a summer groundwater depletion 76% wider than the average summer depletion under baseline conditions. Here, mitigation actions to reduce abstracted volumes, such as transitioning to more efficient irrigation systems, could reduce groundwater vulnerability to climate change. On the other hand, aquifer systems governed by natural recharge and discharge processes showed a wider pluriannual variability associated with dry and wet years and resulted less vulnerable to single dry seasons than highly anthropic systems.