Abstract
Abstract Despite their potential influences on surface water and climate, groundwater processes are generally not represented in climate models. Here, a simple groundwater scheme including two-dimensional flow dynamics and accounting for groundwater–river exchanges is introduced into the global Total Runoff Integrated Pathways (TRIP) river routing model coupled to the Météo-France climate model. This original scheme is tested in offline mode over France at high () and low (0.5°) resolution against a dense network of river discharge and water table observations over the 1970–2010 period, and is compared to the fine-tuned Système d’Analyze Fournissant des Renseignements Atmosphériques à la Neige (SAFRAN)–Interactions between Soil, Biosphere, and Atmosphere (ISBA) coupled hydrometeorological model (MODCOU). In addition, the simulated terrestrial water storage (TWS) variations are compared to the TWS estimates from the Gravity Recovery and Climate Experiment (GRACE) satellite mission. The aquifer basins over France are defined using the World-wide Hydrogeological Mapping and Assessment Programme (WHYMAP) groundwater resources map, a simplified French lithological map, and the International Geological Map of Europe (IGME). TRIP is forced by daily runoff and drainage data derived from a preexisting simulation of the ISBA land surface scheme driven by the high-resolution SAFRAN meteorological analysis. Four simulations are carried out with or without groundwater at both resolutions. Results show that the groundwater scheme allows TRIP to better capture the spatiotemporal variability of the observed river discharges and piezometric heads. Summer base flows are particularly improved over the main rivers of France. Decreasing the horizontal resolution has a limited impact on the simulated discharges, while it slightly degrades the simulation of water table variations.
Highlights
In climate models, the land surface hydrology has a major influence on the terrestrial water and energy budgets and, thereby, on the simulated weather and climate (Dirmeyer 2000, 2001; Douville 2003, 2004; Koster et al 2000, 2002)
E-mail: bertrand.decharme@cnrm.meteo.fr (Gedney et al 2000; Douville et al 2000a,b; Molod et al 2004; Lawrence and Slater 2007; Alkama et al 2008). These land surface processes are parameterized in continental hydrological systems (CHSs) based on two components: 1) the land surface models (LSMs), which provide realistic lower boundary conditions of temperature and moisture in atmospheric general circulation models (AGCMs), and 2) the river routing models (RRMs), which convert the total runoff provided by LSMs into river discharges in order to evaluate the simulated water budget and/or to transfer continental freshwater to the oceans, thereby closing the global hydrological cycle
The main objectives of this paper are to describe an original simple groundwater scheme, to evaluate its influence on the daily river discharges simulated at a relatively high resolution by the Total Runoff Integrated Pathways (TRIP) RRM used at the Centre National de Recherches Meteorologiques (CNRM), and to demonstrate its robustness and suitability for lower-resolution applications using a simple methodology based on available global datasets to estimate the aquifer geometry and parameters
Summary
The land surface hydrology has a major influence on the terrestrial water and energy budgets and, thereby, on the simulated weather and climate (Dirmeyer 2000, 2001; Douville 2003, 2004; Koster et al 2000, 2002) It can affect the temperature and ocean salinity at the mouths of the largest rivers (Durand et al 2011), the water and energy exchanges at the land surface, and the climate, at least at the regional scale (Gedney et al 2000; Douville et al 2000a,b; Molod et al 2004; Lawrence and Slater 2007; Alkama et al 2008). Water table rise and fall can interact with the soil moisture profile and thereby affect evapotranspiration and the land surface energy budget (e.g., Dingman 1994)
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