Development of a Hydrogeological Conceptual Model of the Varaždin Alluvial Aquifer

The Varaždin aquifer represents the main source of water for public supply, agricultural, and industrial purposes in County NW Croatia. In last decades, this area has experienced contamination groundwater with nitrates. This study describes conceptualization purpose developing numerical model flow nitrate transport. Within study, three important elements are defined: geometry, recharge from precipitation, other boundary conditions. 3D revealed that consist layers: upper aquifer, semipermeable interlayer, lower aquifer. Wetspass-M was used assessment spatial temporal distribution balance components period 2008–2017. Results indicate average annual precipitation is distributed as 34% recharge, 21% surface runoff, 45% actual evapotranspiration. maps equipotential lines show behavior system define conditions, i.e., discharge areas aquifer: an inflow Drava River accumulation lake on northwest north, no west south, outflow east.