**Author details**

an isolated high concentration zone (**Figure 8**, right). In other parts of the study region, chloride level also decreased from highest at the west boundary to lowest at east, which was similar to

At the end of 2018 as a prediction of future, chloride levels in layer 1 at the SEF and SWF sprayfields keep decreasing since 2004 but are still about 10 mg/L and still higher than surrounding area (**Figure 9**, left). Chloride concentration at Spring Creek Springs is still the highest in the whole study region. In layer 2, chloride concentration in the north of the SWF sprayfield decreases below 5 mg/L because of the flushing effect (**Figure 9**, right). The west

**Figure 9.** Chloride concentration from the simulation by CFPv2 and UMT3D at the end of 2018 (left: layer 1; right: layer

Groundwater flow in a well‐developed karst aquifer is mainly dominated within the fractures, conduits and caves formed and/or enlarged by carbonate dissolution. In general, most groundwater‐modeling methods, such as MODFLOW‐2000, apply Darcy equation to simulate groundwater flow, in which groundwater flow is laminar in the primary porosity (i.e., matrix porosity) of the aquifer. However, Darcian principle is not applicable in a well‐developed karst aquifer due to the dual permeability properties present in the aquifer. Therefore, advanced methodologies, such as the discrete‐continuum model, should be used to model groundwater

The physically based discrete‐continuum numerical models are widely applied to simulate groundwater flow and solute transport in a karst aquifer with conduit networks. The CFPM1 is able to accurately simulate groundwater flow in karst aquifers. The major hypothesis of this

part of study region still has higher chloride concentration than the east part.

the distribution in 1986.

128 Groundwater - Contaminant and Resource Management

2).

**5. Discussion and conclusion**

flow in karst aquifers.

Bill X. Hu1,2\* and Zexuan Xu2

\*Address all correspondence to: bill.x.hu@gmail.com

1 Department of Ecology, Jinan University, Guangzhou, China

2 Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahas‐ see, FL, USA
