Impact of climate on groundwater levels at a case study in Alentejo, Portugal, considering unsaturated infiltration

¹ IST, DECivil, University of Lisbon, Lisbon, Portugal
² AIR Centre – Atlantic International Research Centre
³ CERIS, Lisbon, Portugal

^* Corresponding author: rafaela.cardoso@tecnico.ulisboa.pt

Abstract

In the context of climate change, the Alentejo region of Portugal is particularly vulnerable, with recharge rates and groundwater levels projected to decline significantly. Local groundwater-dependent ecosystems – notably cork oak forests that rely on deep soil moisture – are therefore at considerable risk. This paper presents results from a research project aimed at developing a flow model for a study site at Herdade de Abegoaria to simulate water dynamics in the vadose zone. The model accounts for unsaturated infiltration based on the soil water retention curve, as well as evaporation processes. Soil samples were collected for laboratory analysis, and monitoring data – including meteorological records and continuous observations of groundwater table fluctuations – were used to calibrate the numerical model through inverse analysis. The calibrated model is then used to simulate future scenarios for the 2020–2100 period under climate change projections, which anticipate significant declines in groundwater levels and potentially severe environmental impacts across the region.