In 2010–2012, the hydrogeological model of Latvia (LAMO) was developed by scientists of Riga Technical University. The commercial program “Groundwater Vistas” is used for running LAMO. In 2013, data provided by LAMO have been used for the mapping of the Gauja/Koiva River basin district. The materials on the mapping have also included information about groundwater flow balances of the district. The flow balances of Latvia and the Gauja district have been considered. The flow balances of groundwater bodies of the district have been analysed. The flow balances provide new knowledge on the complex interaction between surface water (rivers, lakes, sea, precipitation) and groundwater.