Understanding groundwater drivers in the Mediterranean region using a combination of modeling and in-situ data at a regional scale

Abstract

<p>The Mediterranean region is characterised by growing anthropogenic and climate pressures, resulting in increased water demand. Even though groundwater represents a strategic freshwater reserve in the Mediterranean, its status is becoming increasingly uncertain. The uneven distribution of data availability and scant data-sharing policies and systematic monitoring are significant constraints for management and vulnerability assessments. The objectives of this work are: i) characterization of significant changes in groundwater level time series in the region, ii) comparison of groundwater level models with in-situ data, iii) determine the influence of drivers in the temporal changes as well as the spatial distribution of groundwater levels. </p><p>A database has been developed with over 8,000 time series of groundwater levels collected from national monitoring systems of Spain, Portugal and France, concentrating most measurements after 1980. At first, a search for long term trends and temporal patterns is performed on the most complete time series in the 1985-2014 period. Correlations between significant trends and environmental and anthropogenic drivers are assessed. Furthermore, the outputs of three steady-state global groundwater models (Reinecke et al. (2019), de Graaf et al. (2015) and Fan et al. (2013)) are compared to both interpolated grid-based and piezometer observations. And the relationship between the spatial distribution of groundwater level with explanatory variables is characterized.</p><p>Significant groundwater level changes can be found in at least one third of the assessed piezometers. The simulated steady-state hydraulic head obtained from the three models showed a good agreement with the in-situ data in the Iberian Peninsula. A combined analysis of the temporal and spatial drivers for groundwater dynamics at a regional scale will ameliorate groundwater process understanding in the Mediterranean region. This study also makes a case about the importance of consistent and reliable monitoring as a necessary step for management of the resource. </p><p><strong>Acknowledgement: </strong>This work was supported by Sustain-COAST and InTheMED projects. Sustain-COAST - funded by the German Federal Ministry of Education and Research (Grant 01DH19015) under the EU PRIMA 2018 programme. InTheMED - funed by the PRIMA 2019 programme supported by the European Union’s Horizon 2020 research and innovation programme under grant agreement No 1923.</p>