Flow and transport modeling in complex karstic systems can be a demanding challenge. Various modeling approaches have been proposed during the last decades, ranging from black-box lumped to physically-based distributed models. Given this broad variety of tools, which can address a wide range of questions related to flow- and transport processes in karst aquifers, it can be challenging to find appropriate modeling approaches for a given objective. For this reason, several (early career) karst modelers expressed their interest in forming a joint working group. The proposed group aims to provide a platform for young karst scientists to address questions related to existing model tools, talk about their strengths and weaknesses and discuss specific modeling tasks with more experienced modelers. Moreover, this collaborative group seeks to discuss open research questions and future directions in karst modeling. Therefore, we encourage early career modelers dealing with questions related to karst systems to join our initiative during the EGU conference 2020.