Groundwater circulations between alluvial aquifer and underlying senonian chalk in the Seine Valley

Hundred kilometres upstream from Paris, on the confluence of the Seine and Aube rivers, riverine wetlands expand every year, resulting of flooding and /or upward movement of water in aquifers. In this region, the groundwater s ystem is made up of an alluvial aquifer (alluvial deposits are Neogene-Quat ernary) that fits into an underlying senonian chalky aquifer. In the alluvi al aquifer, the water level is 2 m below the soil during the major part of the year but has been recorded far from the surface and sometimes above the surface in winter. This paper report the water circulations between those aquifers on an interannual scale. We thus pointed up a contribution of wate r of 400 Mm(3).yr(-1) from the Senonian aquifer to the alluvial aquifer, an d a residence time of water in the alluvial deposits of about 2 years. Fina lly, those values have been corroborated by a modelisation of the Senonian aquifer using MODFLOW. (C) 1998 Elsevier Science Ltd. All rights reserved.