The Hydrogeological Model of Latvia LAMO4 as a Tool for Investigating the Processes of Nature. Sources of Groundwater Inflow for the Iecava River

Abstract

In 2010–2012, the hydrogeological model (HM) of Latvia (LAMO) was established by the scientists of Riga Technical University (RTU). In 2013–2014, LAMO was upgraded. In 2015, the recent version LAMO4 was developed. In LAMO4, the plane approximation step was decreased from 500 meters to 250 meters. The base flows of rivers for HM were adjusted by accounting for data that were provided by the measurements of river streams. LAMO is run by the commercial program Groundwater Vistas (GV), version 6. It contains the MODFOW and MODPATH programs for supporting HM and for tracking groundwater particles, respectively. By using MODPATH, the case of the Iecava river was investigated in order to find the sources that support groundwater inflow into the river (its base flow). Unforeseen results were obtained. Due to the appliance of the large regional HM, it was discovered that some part of the river base flow comes from the areas that are located very far from the river drainage basin. It also was not expected that even within the basin the particle traces were very complex. The results described in the paper serve as demonstration for the usefulness of applying a large complex HM for investigating the processes of nature.