Characterization of soil drainage dynamics on karst terrains by developing a site-specific reservoir cascade scheme hydrological model with preferential flows

Models provide quantitative solutions that enable better understanding of karst soils hydrology. A location in central Spain was selected to implement a 1-D hydrological model that uses a reservoir cascade scheme (RCS) approach to simulate soil water content (SWC) at daily resolution. The model simulates SWC for six soil layers and includes additional modules to reproduce preferential flow regime. The soil profile in the model is 0.5 m deep, developed in silt loam soil on top of dolomite marbles. Three different configurations of the model were considered. Configuration 1 considers a basic RCS module, whereas other configurations include preferential flows. Thus, Configuration 2 considers RCS module together with a continuous preferential flow module, where 1 to 5% of available SWC from each layer is drained every day along preferential pathways. Configuration 3 contains a discontinuous preferential flow module in addition to previous modules. The discontinuous prefer-ential flow is only activated during rainfall events occurring after long dry periods. Simulated SWC values are compared with measured SWC values, so model parameters are iteratively adjusted to optimize the model re-sults. The model produces the best simulations implementing the Configuration 3, when matrix flow and two preferential flow regimes are considered. The model shows that preferential flows significantly contribute to recharge and should not be neglected in soil hydrological models and recharge estimations in karst areas.

Automated summary

This study used a 1-D hydrological model to simulate soil water content in a location in central Spain. The results showed that preferential flows significantly contribute to recharge and should be considered in soil hydrological models and recharge estimations in karst areas.