Maria Novo (Portugal) 1; Manuel Oliveira (Portugal) 1; Tiago Martins (Portugal) 1; Maria José Henriques (Portugal) 1
1 - LNEC
Climate change studies usually have long term time horizons (2050 or 2100) while decision-makers define policies under short term frameworks. To help decision-makers set up adaptation policies, BINGO project analysed the impacts of climate change, including extreme events, on the water cycle for time horizon 2024. Climate change impacts on groundwater for 3 large aquifers in Tagus Basin (Aluvies do Tejo, Tejo-Margem Direita & Tejo-Sado/Margem Esquerda) were analysed in BINGO Portuguese case-study. For each of the 10 climate realizations and the ensemble of these realizations, generated by regional climate model MiKlip developed by FUB, aquifer recharge scenarios were determined using BALSEQ_MOD (a sequential daily water budget develop in LNEC). Of these 11 recharge scenarios 3 were chosen – ensemble (R1_R10), maximum (R1), minimum recharge (R3) – and fed into the 3D aquifer flow model (FEFLOW) which generated the piezometric surfaces for each of these scenarios.
Drought impacts were also analysed, under transient state. This methodology can be used anywhere as long as recharge values obtained from climate projections and robust data to build the flow model (for porous aquifer) exist. Results show the piezometry for ensemble scenario does not change significantly from present day values. R1 scenario shows piezometry rises of <2 m up to 5 m in general with several flooded areas. R3 scenario shows piezometry declines of <2 up to 10 m in general and no flooded areas. Multiannual drought scenarios (5 year drought) show a piezometry decline of 2 to 3 m in general. From the results, impacts seem mild for the short term time horizon of 2024, in particular for droughts, pointing to a much required paradigm shift of policy-makers concerning adaptation policies. Instead of looking and acting for the near future, policy-makers must start now create adaptation policies based also on long term projections.