Multi-model comparison of a major flood in the groundwater-fed basin of the Somme River (France)

Abstract

Abstract. The Somme River Basin is located above a chalk aquifer and the discharge of the somme River is highly influenced by groundwater inflow (90% of river discharge is baseflow). In 2001, the Somme River Basin suffered from a major flood causing damages estimated to 100 million euro (Deneux and Martin, 2001). The purpose of the present research is to evaluate the ability of four hydrologic models to reproduce flood events in the Somme River Basin over an 18-year period, by comparison with observed river discharge and piezometric level as well as satellite-derived extents of flooded area. The models used differ in their computation of surface water budget and in their representation of saturated and unsaturated zones. One model needed structural modification to be able to accurately simulate the riverflows of the Somme river. The models obtained fair to good simulations of the observed piezometric levels, but they all overestimate the piezometric level after flooding, possibly because of a simplistic representation of deep unsaturated flow. Models differ in their annual partition of the infiltration of water within the root zone (mostly driven by simulated evapotranspiration), but these differences are attenuated by water transfers within the saturated and unsaturated zone. As a consequence, the inter-model dispersion of the computed annual baseflow is reduced. The aquifer overflow areas simulated during flooding compare well with local data and satellite images. The models showed that this overflow occurs almost every year in the same areas (in floodplain), and that Correspondence to: F. Habets florence.habets@mines-paristech.fr the flooding of 2001 was characterized by an increase in the quantity of the overflow and not much by a spreading of the overflow areas. Inconsistencies between river discharge and piezometric levels suggest that further investigation are needed to estimate the relative influence of unsaturated and saturated zones on the hydrodynamics of the Somme River Basin.

Groundwater and Surface Water Interaction at the Regional-scale – A Review with Focus on Regional Integrated Models

“…They are often developed by national -Zhangye basin, China, 9,097 km 2 (Tian et al, 2015) (Wilcox et al, 2007) MODCOU / EauDyssée Saleh et al (2011) Pryet et al (2014) ? SAM model (Ledoux et al, 1989;Ledoux et al, 1984) RAPID, 1D Muskingum scheme (David et al, 2011) 1D Stream network hydraulic modelling HEC-RAS (Saleh et al, 2011) Conceptual model soil water-budget (Pryet et al, 2014) -Seine basin, France, 95,600 km 2 (Ledoux et al, 2007) -Rhône basin, 86,500 km 2 (Etchevers et al, 2001) -Upper Rhine basin, 13,900 km 2 (Thierion et al, 2012) -Somme basin, 6,433 km 2 (Habets et al, 2010;Korkmaz et al, 2009) (2000) Kim et al (2008) ? MODFLOW (river package) SWAT (Arnold et al, 1993;Arnold and Fohrer, 2005) Not represented (Sophocleous et al, 1999) Musimcheon Basin, South Korea, 198 km 2 (Kim et al, 2008) WaSiM, WaSiM-ETH Krause and…”

Reporting of Stream-Aquifer Flow Distribution at the Regional Scale with a Distributed Process-Based Model

“…This platform has successfully simulated surface and groundwater flow in many basins of various scales and different hydrogeological settings, such as the Seine basin, 76 375 km 2 (Gomez et al 2003;Ledoux et al 2007;Saleh et al 2011), the Rhône basin, 87000 km 2 (Etchevers et al 2001), the Upper Rhine basin, 13 900 km 2 (Thierion et al 2012), the Somme basin, 6433 km 2 (Habets et al 2010;Korkmaz et al 2009) and the Loire basin, 117 500 km 2 (Monteil 2011). This study is also based on the Eaudyssée platform, but we extended the method for stream-aquifer coupling and provide for the first time, practical considerations for the description of stream aquifer flow (Section 2.2).…”

A critical assessment of simple recharge models: application to the UK Chalk

“…One of the problems with using tracers, especially in dual permeability systems, is that the same chemical profile could be consistent with multiple conceptualisations (a classic example is the reinterpretation of the results of Smith et al, 1970, by Foster, 1975, discussed in Mathias et al, 2005. Methods based on physical measurements include: soil water balances (Rushton, 2005;Ragab et al, 1997;Finch, 1998); solutions to some form of 1-D Richards' equation involving soil moisture and/or matric potential observations (van den Daele et al, 2007;Brouyère, 2006;Habets et al, 2010;Ireson et al, 2009b;Ireson and Butler, 2011); and water table fluctuations (Cuthbert, 2010;Ireson et al, 2012). All of these methods have limitations, which may or may not be prohibitive for a given field site.…”

“…There is a long history of research into the physical processes that control recharge to the unconfined Chalk aquifers of northwestern Europe, particularly in the UK (see reviews in Mathias et al, 2006;Ireson et al, 2009b;van den Daele et al, 2007 andButler et al, 2012), France (Habets et al, 2010) and Belgium (Brouyère et al, 2004;Brouyère, 2006). The work in these citations and others Ireson et al, 2012) has focused on developing physically based models, and using these models to reproduce field observations.…”