The Karst Modelling Challenge (KMC) was set up by Pierre-Yves Jeannin (SISKA) at the Eurokarst 2016 conference in Neuchatel (Switzerland) with the aim of identifying the most effective approach for modelling karst aquifers in different situations. As such, competing teams have been given access to the same rainfall-discharge measurements from the Milandre cave stream catchment in Switzerland and asked to model the aquifer behaviour using their own preferred approach. The Milandre catchment is approximately 10 km2 large, receiving only autogenic recharge and discharges at the Saivu spring. Although around 30 teams showed initial interest in the KMC, only 8 teams actually submitted models for the Phase 1 of the challenge which was to model the spring flows in time for the Eurokarst 2018 conference held last week in Besancon (France) – 3 teams from Germany, 2 from France, 1 from Switzerland, 1 from Spain and 1 from Ireland. The Irish team is three iCRAG researchers based in TCD - Laurence Gill, Philip Schuler and Lea Duran. The Phase 1 models were compared at the Eurokarst conference with 3 considered to be fairly simple lumped parameter models, 3 as semi-distributed models and 2 as fully distributed models. The iCRAG team’s approach has been to develop a hydraulic / hydrological semi-distributed pipe network model of the karst aquifer system. The results of Phase 1 showed that the iCRAG team were placed in 4th positon out of the 8 teams for the flow modelling exercise. The next Phase is to model head levels across the aquifer.