Abstract
Integrated hydrological modelling (IHM) can reliably characterize surface-water/groundwater interactions in complex hydrological systems such as hard-rock systems (HRS), located in water-limited environments (WLE). Such HRS-WLE conditions are represented by Sardon catchment (~80 km2) in Spain, where the MODFLOW 6 modelling environment was tested, applying the following improvements as compared to previous works in that catchment: a new conceptual model, driving forces redefined based on remote sensing data, an unstructured Voronoi grid, and, most importantly, a novel cascade-routing and reinfiltration (CRR) concept. In the standard MODFLOW 6, rejected infiltration and groundwater exfiltration have always been considered as sinks (evaporation). However, in reality, that water can not only evaporate but also reinfiltrate back to the subsurface or move as runoff towards drainage water bodies. The CRR improves surface–unsaturated-zone interactions and also surface-water/groundwater interactions. The standard and new capacities of MODFLOW 6 are presented in the transient model of the Sardon catchment, calibrated using 7 years of daily groundwater heads and streamflows. The results showed: the large spatio-temporal variability of the groundwater fluxes, the substantial role of groundwater exfiltration, the low catchment storage, the fast reaction of the water table and streams to rainfall, and the mosaic character of the net recharge. These characteristics are typical for HRS-WLEs with a shallow water table. MODFLOW 6 has many improvements compared to previous MODFLOW versions, so with the proposed CRR concept (still can be improved), the single-environment MODFLOW 6 has modelling capacity comparable with multienvironment IHMs, while being more flexible and more efficient.
Highlights
Aquifers of hard-rock systems (HRSs) have not been given as much attention as other aquifer types, likely due to their low productivity and difficulties in water-well drilling (Singhal and Gupta 2010)
The research proposed in this study aims to: (1) implement the novel cascade-routing and reinfiltration (CRR) concept in MODFLOW 6, as to the authors’ knowledge, it is the only Integrated hydrological modelling (IHM) that allows for implementing such concept; (2) design and compute a detailed water balance, applying CRR, in MODFLOW 6; and (3) investigate the dynamics of the surface-water/groundwater interactions in the HRS-water-limited environments (WLE), applying new MODFLOW 6 modelling tools
The Sardon catchment is an area suitable to investigate dynamic processes of surface-water/groundwater interactions so to test related novel concepts and tools such as those applied in this study because of: (1) an excellent database with long time-series automated measurements; (2) hydrological complexity with distinct and fast surface-water/groundwater interactions due to: (a) shallow water table, low storage and high hard-rock permeability; (b) Mediterranean water-limited environment (WLE) with clear wet and dry seasons and savannah oak woodland interacting with groundwater; and (c) dense drainage network, hydraulically connected with the aquifer system; and (3) remoteness of the study area, implying negligible human impact on hydrological processes
Summary
Aquifers of hard-rock systems (HRSs) have not been given as much attention as other aquifer types, likely due to their low productivity and difficulties in water-well drilling (Singhal and Gupta 2010). There is a continuous need for improving the assessment of groundwater resources in HRSs, to more efficiently extract. The HRSs are characterized by generally low groundwater storage and spatially variable hydraulic conductivity due to their weathered fractured-rock composition and large heterogeneity. In HRSs, groundwater flow occurs mainly due to the secondary porosity, i.e. faults and fractures, and is largely dependent on their density and connectivity. The low aquifer storage and typically shallow impermeable rock basement, so shallow drainage base, imply that the HRSs are characterized by a shallow groundwater table, dense drainage networks and related short groundwater residence time associated with short flow paths (Hassan et al 2014). The challenge in dealing with the HRSs is their complexity of surface-water/groundwater interactions and the related difficulties in simulation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
