Figure 4 - uploaded by Séverin Pistre
Content may be subject to copyright.
"Gilbert delta" genetic model (Clauzon et al., 1990). -The continental Pliocene aquifer (topset beds) Prograding fluvial sands filled the distributary channels of the deltaic complex and covered the marine sands, forming this aquifer. It contains excessive water mineralisation in the northern part of the basin, along the lagoon and even more along the coast at Barcares.
Context in source publication
Context 1
... characteristics of the system are linked to the Messinian event: (i) digging out of huge canyons during the Messinian Salinity Crisis (5.9 -5.3 My), during which the mean sea level dropped down to 1500 m below present mean sea level (pmsl), and (ii) filling-up of these canyons, after the sea level rise up to 80 m above pmsl (5.3 -3.8 My) (Hardenbold et al, 1998), with the marine and fluvial sands that constitute the two main Pliocene aquifers. The sediments settled according to the "Gilbert delta" genetic model (Figure 4). The aquifer is very productive, especially in the Salanque plain, with a transmissivity of 10 -2 to 3×10 -2 m 2 /s (T = 10 -4 m 2 /s at the edge of the aquifer). ...
Citations
... Geology The sedimentary basin of the Roussillon plain is the result of the filling of the Gulf of Lion (south of France, Mediterranean region) after the erosion process that affected the Mediterranean basin during the Messinian crisis Page 3 of 20 201 (Clauzon et al. 2015). This filling occurred following a Gilbert delta structure (Gilbert 1890) in a prograding-aggrading system during the Pliocene (Aunay et al. 2004;Duvail 2008;Clauzon et al. 2015). This sedimentological setting results in a superposition of many prisms composed of clay in the distal parts (bottomsets) and sands in the proximal parts (foresets). ...
... Seismic campaigns and hydrogeological tests indicate that these paleochannels are likely to be spatially well connected, creating an important available groundwater resource (Dall'Alba et al. 2020). The SMP bottom formation is generally considered to be rather homogeneous and highly permeable (Chabart 1996; Aunay et al. 2004). ...
... The PA appears to be confined over most of the plain due to the fact that its permeable layers are generally embedded into clay rich formations having a low vertical permeability (Chabart 1996; Aunay et al. 2004). Locally, the PA outcrops over the western part of the plain and can thus be unconfined, but for simplicity, we assume they are confined. ...
Global climate change-induced stresses on coastal water resources include water use restrictions, saline intrusions, and permanently modifying or damaging regional resources. Groundwater in coastal regions is often the only freshwater resource available, so an in-depth understanding of the aquifer, and the aquifer’s response to climate change, is essential for decision-makers. In this study, we focus on the coastal aquifer of Roussillon (southern France) by developing and investigating a steady-state groundwater flow model (MODFLOW 6) and calibrated with PEST++ on a Python interface (FloPy and PyEmu). Model input and boundary conditions are constrained by various scenarios of climate projections by 2080, with model results predicting the aquifer’s response (and associated uncertainty) to these external forcings. Using simple assumptions of intrusion estimates, model results highlight both strong climatic and anthropogenic impacts on the water table. These include aquifer drawdowns reaching several meters locally, and the seawater interface advancing locally several hundred meters inland and rising by several meters. Intrusions of this magnitude risk endangering exploited water wells and their sustainability. Our results demonstrate the critical importance of properly characterizing the geology and its heterogeneity for understanding aquifers at risk because poor predictions may lead to inappropriate decisions, putting critical resources at risk, particularly in coastal environments.
... In this context, the Llobregat delta is an ideal place to study the stratigraphic architecture and the effects to groundwater flow ( Vázquez-Suñé et al., 2006; Gamez, 2007). For proper management of the resources an understanding of the onshore and offshore delta architecture is required (Water Framework Directive, 2000;Ehman et al., 2000;Edwards and Evans, 2002;Aunay et al., 2004; Gamez, 2007). Some studies focus on Postglacial and Holocene onshore-offshore correlation (Gensous and Tesson, 2003;Boyer et al., 2005;Fielding et al., 2005;Labaune et al., 2005a;Lobo et al., 2005a;Tesson et al., 2005). ...
A flow and mass transport mathematical model has been calibrated to simulate piezometric head and chloride evolution in the Llobregat delta confined aquifer. A twenty-year period (1965–1985) is simulated with monthly time steps. Automatic estimation of flow and transport parameters are obtained by means of a code that simulates flow and mass transport of constant density fluids. In this case, density differences owing to groundwater salinity changes by marine intrusion can be neglected because the aquifer thickness is relatively small and because both the horizontal density gradient and the aquifer dip are small. Calibration of the flow problem leads to an excellent fit between measured and computed heads, which, however, can be obtained with different transmissivity patterns. When switching to the transport problem, best results in terms of concentration fits are obtained by associating the seawater intrusion plumes with high transmissivity zones that can be attributed to palaeochannels. In short, transient head and concentration data have been used jointly for automatic calibration of a regional model, which has proven advantageous both because it facilitates model selection and because it has led to a model with an improved conceptual basis.
Groundwater resources in deltaic aquifers are essential in the Mediterranean region to sustain the socio-economic development of coastal communities and shallow-water ecosystems. Understanding the geological connection between coastal aquifers and the offshore sedimentary record is important to better predict consequences in terms of water management. In spite of this, most approaches to Postglacial and Pleistocene deltaic sedimentation focus either on the offshore or the delta plain; few studies correlate and integrate the entire system. In the Llobregat delta (south of Barcelona, Spain), onshore–offshore correlation is achieved by integrating data from sediment cores acquired on the deltaic plain with seismic profiles from offshore. Data integration enables the reconstruction of the entire deltaic system, providing a more well-defined picture and a better understanding of the onshore–offshore stratigraphic framework in a Late Quaternary, tectonically active narrow shelf in the western Mediterranean Basin.
