A theoretical model for simulating periodic processes of intermittent karst springs considering changed recharge rates into siphon cavity.

• A theoretical model was proposed to simulate discharge periodic variation. • The model was verified by physical experiments and applied extensively. • The model reveals the relationship between water level and discharge periods. • The model can estimate the permeability coefficient according to periodic changes. Intermittent karst springs (IKS) are common phenomena in karst areas where spring flow rates rise and fall in variable periods, which is generally attributed to the siphon structure in karst aquifers. However, the previous model assumed that the siphon cavity received a fixed recharge rate, thus the IKS showed a fixed periodic characteristic. In this study, an improved theoretical model (IKS model) was proposed to simulate the hydrological process of IKS with changing periods by considering the varying recharge rate from aquifers to the siphon cavity. The model uses two tandem tanks to represent the karst aquifer and siphon cavity separately. The numerical solution was obtained by the iterative method to predict the periodic variations of flow rate and eruption time of IKS. The IKS model was verified by physical experiments under four representative recharge conditions, showing good consistency between theoretical and experimental results. It reveals the hydrologic processes mechanism of the IKS by quantitatively describing the relationship between the cycle period of the IKS discharge variations and the flow exchanges in the siphon cavity-aquifer system. Furthermore, this model performs well in simulating the hydrological process of Chaoshuidong Spring in central China and approximately estimated the hydraulic coefficient of the aquifer in the basin based on observed periodic changes in spring discharge. These findings might be essential for the development, management, and protection of groundwater resources in IKS. [ABSTRACT FROM AUTHOR]