Large-scale hydrologic models exist for prediction and management of water resources. These models typically do not explicitly consider the particularity of karst hydrology, which is crucial to capture the characteristics of hydrologic responses in karst regions. Most of the studies in karst regions focus on recharge areas and karst spring systems at the aquifer scale. Few studies have investigated the interaction of karst springs and streams at the catchment or even larger scales. Therefore, how to adequately combine karstic and non-karstic characteristics in model still needs to be understood. In this study, we introduce a systematic approach for conceptual model development at the aquifer and catchment scales to investigate appropriate model structure(s) that integrate karstic and non-karstic properties. Firstly, six pilot catchments around Europe and Mediterranean have been selected to implement the approach. Every pilot catchment has both streams and karst springs with discharge observations over 10 years. These pilot catchments are small to large size with low to high karst coverage and cover different landscapes and climates. We use a new observation-based approach to develop a conceptual model as a specific guidance for the selection of the most appropriate numerical model structure(s). In order to combine surface catchment and recharge area, the calculation of a new metric, the Lateral Flow Index, is necessary to quantify differences between topographic and subsurface catchment areas. Finally, based on the conceptual model, we will explore the most appropriate model structure(s) that account for the identified relevant processes of our test sites. We benchmark the usefulness of our results at the catchment scale by comparing them with the results of an existing HBV model that does not explicitly include karst features. This study will give insights to the knowledge gap of the combination of karstic and non-karstic hydrologic processes into one model and will provide directions for modelling water resources availability at karst regions at a large scale.