The dynamics of groundwater chemistry in unconsolidated aquifers: the Salland section

Hydrological models alone can be ambiguous in the determination of flowpatt erns and groundwater ages. Their use is thus somewhat limited in the study of controls and spatial distribution of groundwater compositions. Multileve l wells can be useful for the understanding of local groundwater flow and f or model verification. The dynamics of groundwater chemistry over a period of seven years is studied in a section of multilevel wells in an unconsolid ated aquifer in the eastern part of the Netherlands. From chemistry-depth p rofiles important information concerning hydrological systems, age of the w ater and local flow direction (seepage or infiltration) is deduced. The new concept of systemfunnels, funnel-shaped ground water volumes that originat e from geochemically homogeneous areas, provide a framework for the descrip tion of the dynamics of groundwater chemistry. Short-term predictions of wa ter chemistry trends are made and boundaries between local and regional gro undwater flow systems are identified. Chemical variations along the flowpat h are related to the hydrochemical changes in the last two centuries in the recharge areas. The development history of a region is thus an essential f actor in the evolution of the groundwater chemistry. (C) 1999 Elsevier Scie nce Ltd. All rights reserved.