Impacts of climate change on groundwater – results from the BINGO project

Abstract

Climate change impacts on groundwater usually take a longer time-lag to occur than in surface water resources, depending on the inertia of the aquifer, which are further enlarged by land use changes, population growth, changing socio-economic conditions, hindering the sustainable management of groundwater resources, which should also take into account the ecosystems’ needs. Climate change studies usually are long term (2070 or 2100) while decision-makers define policies under short term frameworks. Trying to overcome this problem, BINGO project analysed the impacts of climate change, including extreme events, on the water cycle for time horizon 2024. The analysis of climate change impacts on the aquifers Tejo-Margem Direita & Tejo-Sado/Margem Esquerda, Aluviões do Tejo (downstream Tagus Basin), starts by using climate data from 10 climate realizations and their ensembles, generated by regional climate model MiKlip developed by FUB. These data are used by BALSEQ_MOD model to calculate recharge, which is an input data for the 3D FEFLOW aquifer’s flow model. Results are presented for maximum recharge conditions (from MiKlip R1 realisation), which show a recharge change of +49.1%, +37.6%, +29.4%, for each of the aquifers, respectively. This is translated in piezometric rises between +2 and +5 m and flooding of several areas. For the minimum recharge conditions (from MiKLIP R3 realization) recharge changes range from -10.4%, - 20.6%, -11.6% respectively for the same aquifers, translated into piezometric changes between -2 and +10 m. For the ensembles recharge conditions (from MiKlip R1_R10) ranges from + 5.4%, + 4.2%, +0.2% respectively, translated into a negligible piezometric change. Once the ensembles scenario is the most likely for 2024 the results show that studies for the short range are not very useful in supporting adaptation strategies, particularly for large aquifers as in this case, and instead what is required is a policymakers’ paradigm shift from the short range to the long range when dealing with climate change. That means, act now in order to be able to cope with the changes that are in store for the future instead of relying only on short term studies.