Novel approaches in sub-surface parameterisation to calibrate groundwater models

Advancement towards improved configuration of pilot point into a model in parameterisation step of groundwater modeling is required to accurately obtain a satisfactory model performance. Nevertheless, the recommendations provided by the majority of current studies on this geostatistical technique are considered too empirical than practical to be applied on real catchment conditions. In this study for the first time a practical approach of using geometric features of pilot point and catchment area is proposed to efficiently configure pilot point distribution in the calibration step of a groundwater model. Three user-friendly ratios, i.e. distance-area (d/A), distance-x grid length (d/Xgrid), and distance-y grid length (d/Ygrid) are introduced in Grid-based (GB) distribution technique. Eight models of eight different pilot point distances (250 m, 500 m, 750 m, 1000 m, 1250 m, 1500 m, 1750 m and 2000 m) were developed using GB technique were constructed on an eogenic karst catchment in Rote Island, Indonesia and their performances were evaluated. Modelers can use the three practical ratios when calibrating groundwater models given the same sub-surface characteristics. This study also provides some insights into the trade-off between maximising and restricting the number of pilot points and offers a relative basis for selecting pilot point properties and distribution method in the development of a physically-based groundwater model.