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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Discussion papers
https://doi.org/10.5194/hess-2018-626
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/hess-2018-626
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 18 Jan 2019

Submitted as: research article | 18 Jan 2019

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Hydrology and Earth System Sciences (HESS).

Groundwater influence on soil moisture memory and land–atmosphere interactions in the Iberian Peninsula

Alberto Martínez-de la Torre1,a and Gonzalo Miguez-Macho1 Alberto Martínez-de la Torre and Gonzalo Miguez-Macho
  • 1Nonlinear Physics Group, Faculty of Physics, Universidade de Santiago de Compostela, Spain
  • anow at: Centre for Ecology and Hydrology, Wallingford, United Kingdom

Abstract. Groundwater plays an important role in the terrestrial water cycle, interacting with the land surface via vertical fluxes through the water table and distributing water resources spatially via gravity-driven lateral transport. It is therefore essential to have a correct representation of groundwater processes in land surface models, as land-atmosphere coupling is a key factor in climate research. Here we use the Land Surface and Groundwater Model LEAFHYDRO to study the groundwater influence on soil moisture distribution and memory, and evapotranspiration (ET) fluxes in the Iberian Peninsula over a 10-year period. We validate our results with time series of observed water table depth from 623 stations covering different regions of the Iberian Peninsula, showing that the model produces a realistic water table, shallower in valleys and deeper under hilltops. We find patterns of shallow water table and strong groundwater–land surface coupling over extended interior semi-arid regions and river valleys. We show a strong seasonal and interannual persistence of the water table, which induces bimodal memory in the soil moisture fields; soil moisture remembers past wet conditions, buffering drought effects, and also past dry conditions, causing a delay in drought recovery. The effects on land-atmosphere fluxes are found to be significant, on average over the region, ET is 17.4 % higher when compared with a baseline simulation with LEAFHYDRO's groundwater scheme deactivated. The maximum ET increase occurs in summer (34.9 %; 0.54 mm day−1). The ET enhancement is larger over the drier southern basins, where ET is water limited (e.g. the Guadalquivir basin and the Mediterranean Segura basin), than in the northern Miño/Minho basin, where ET is more energy limited than water limited. In terms of river flow, we show how dry season baseflow is sustained by groundwater originating from accumulated recharge during the wet season, improving significantly on a free-drain approach, where baseflow comes from water draining through the top soil, resulting in rivers drying out in summer. Convective precipitation enhancement through local moisture recycling over the semiarid interior regions and summer cooling are potential implications of these groundwater effects on climate over the Iberian Peninsula. Fully coupled land surface and climate model simulations are needed to elucidate this question.

Alberto Martínez-de la Torre and Gonzalo Miguez-Macho
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Alberto Martínez-de la Torre and Gonzalo Miguez-Macho
Alberto Martínez-de la Torre and Gonzalo Miguez-Macho
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Short summary
Over semi-arid regions, it is essential to have a correct representation of the groundwater processes in climate modelling. We present a Land Surface and Groundwater Model that incorporates groundwater–soil interactions, groundwater–rivers flow and lateral transport at the subsurface. We study the groundwater influence on soil moisture distribution and memory, and on evapotranspiration in the Iberian Peninsula. Shallow water table regions persist and provide water to the surface during droughts.
Over semi-arid regions, it is essential to have a correct representation of the groundwater...
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