A reservoir model is developed to characterize the functioning of the karst aquifer of the Jinci Spring. It is based on the relationship of the groundwater storage deficit and the groundwater level. The relationship is derived from the monitoring data of the aquifer. The model is verified with the monitoring data (1981-2006). The results show that the reservoir model can describe the character of karst development and the heterogeneity in vertical direction. The model takes account of the artificial recharge, pumping and coal mine drainage, and can simulate the spring discharge, karst groundwater level and the storage deficit accurately at an annual time scale. The model is suitable for macroscopic groundwater management.