Parameterisation of physical models to configure subsurface characteristics of groundwater basins

Owing to its simple procedures, the Head-guided Zonation (HGZ) method can be applied in parameterisation step of groundwater modelling to configure subsurface characteristics of areas where spatial subsurface data is scarce. This method principally employs accessible groundwater level data to divide the area of interest into several zones, for which values of subsurface properties, i.e. hydraulic conductivity and specific yield are assigned. However, current studies provide no guideline on how to effectively divide the zones using head contours to achieve robust model performance. This paper presents development and performance assessments of four HGZ models using four different contour spacings, 30 m, 40 m, 50m and 60m on an eogenetic karst catchment in Rote Island, Indonesia. For the first time, three user-friendly ratios, 'area - head contour interval (A/ci)', 'x grid length - head contour interval (x(grid)/ci)' and 'y grid length - head contour interval (y(grid)/ci)', are introduced as a basis to effectively divide model domain into zones. This study demonstrates that through proper selection of the three ratios in HGZ method a robust parameterisation of subsurface characteristics in groundwater modelling can be achieved.