The Tanralili Sub-Watershed (278.39 km²) in the Maros River Basin, South Sulawesi, Indonesia, is a tropical monsoon catchment with steep terrain and clay-rich, very low-permeability soils, which promote rapid surface runoff during short-duration high-intensity storms. We evaluated the plot-scale hydrological performance of Lubang Sumur Resapan (LSR) and Lubang Resapan Biopori (LRB) using controlled inflow experiments on two representative land-cover plots (secondary dryland forest and mixed dryland agriculture). The experiments were supported by soil texture characterization and design-storm intensity estimation using the Mononobe–Kawakami relationship. Return-period scenarios were used to contextualize event-scale conditions, without applying a fully distributed watershed model. Under very low-permeability conditions (P-4 class; site-mean Ks ≈ 0.00077 cm/s for the tested plots), LSR primarily functions as event-scale detention with gradual seepage. Relative to untreated controls, LSR increased infiltration by ∼77 % and reduced surface runoff by ∼23 % across the tested scenarios, while combined LSR–LRB further improved infiltration and delayed runoff initiation, with the strongest benefits under higher-intensity events. The agricultural plot exhibited earlier runoff onset and higher untreated runoff than the forest plot under identical intensity–duration scenarios, highlighting strong land-cover control on runoff generation at the plot scale. These results provide practical, site-specific benchmarks to guide screening-level siting and maintenance-aware deployment of infiltration interventions in steep, clay-rich monsoon sub-watersheds in Indonesia • Infiltration wells (LSR) increased water infiltration by up to 77 % in clay soils. • Biopore systems (LRB) combined with LSR reduced runoff volume by 31 %. • Peak runoff was delayed and infiltration sustained under extreme rainfall events. • Most significant hydrological gains were found in dryland agriculture and open land. • A spatially optimized MAR framework was developed for tropical monsoon watersheds.
Nanda et al. (Fri,) studied this question.