The determination of groundwater flow system using several deterministicand classical methods in Limboto-Gorontalo Lowland, Gorontalo Province

The Limboto-Gorontalo lowland is the recharge area of the Gorontalo Groundwater Basin in Gorontalo Regency. There has been a considerably wide gap, with floods during rainy seasons but water crisis in dry seasons, which creates animbalanced spatial distribution of groundwater. For this reason, groundwater flow system analysisisnecessary for efficient water resource planning and management. This research was designed to compare several deterministic methods and evaluate how deterministic and classical methods could identify and map the spatial distribution of the groundwater flow system in the Limboto-Gorontalo lowland. This system was determined by monitoring and measuring 157 samples of dug wells. The obtained data were interpolated using two GIS-based deterministic methods, namely inverse distance weighted (IDW) and radial basis function (RBF), and one classical technique, i.e., manual three-point problem method (3PM). Mean absolute error (MAE) and root mean square error (RMSE) values were used to evaluate and decide the best interpolation method. After comparing MAE and RMSE values and analyzing the resulting maps, the RBF was proven to be better than the IDW method. Moreover, the maps generated by RBF and 3PM did not differ significantly. The spatial analysis results showed that the groundwater flow system in the study area originated in the hilly areas in the north and south of Lake Limboto and flew to several valleys and rivers instead of directly accumulating in this lake.