Effects of the conduit network on the spring hydrograph of the karst aquifer

- MODFLOW-CFP is used to simulate a simple karst aquifer.
- The influence of conduit network on the spring hydrograph is discussed.
- The turbulent conduit network only influences the early spring recession behavior.
- The whole spring recession behavior is influenced by the laminar conduit.

SummarySpring hydrograph, especially the recession curve, is widely used to understand the internal information of the karst aquifer. However, how the turbulent conduit network influences the spring hydrograph is still unclear. Generally, the spring hydrograph could be divided into the early portion from the point recharge and late portion from the diffuse recharge. In this paper, MODFLOW-CFP is used to understand the influence of turbulent conduit on the spring hydrograph from the diffuse recharge and different influences of the turbulent and laminar conduit on this spring hydrograph. And then, a conceptual model is used to further interpret it. Based on the analysis results, the influence of turbulent conduit on the spring hydrograph from the point recharge is also discussed. For the spring hydrograph from the diffuse recharge, when ignoring the storage variation of the conduit network, the turbulent conduit just influences the early recession curve and this influence decreases with the spring discharge or rainfall intensity until it disappears. When the spring hydrography is strongly reshaped by the storage of the turbulent conduit network, only the early recession behavior is influenced by the turbulent conduit network as well. However, the laminar conduit network has a strongly influence on the whole recession behavior. The late exponential recession coefficient decreases with the conduit diameter and conduit storage. These different influences of turbulent and laminar conduit on the spring hydrograph are mainly caused by their different flow characteristics. Although the turbulent conduit could also strongly influence the early spring hydrograph from the point recharge, the late spring hydrograph is mainly controlled by diffuse recharge and the influence from the turbulent conduit may also disappear.