Comparative streamflow recession dynamics in five tropical monsoonal catchments: implications for adaptive river basin management

Streamflow recession integrates catchment-scale water depletion, yet its interpretation in tropical monsoonal catchments is complicated by event variability, aggregation effects, and declining observational support. We compared five catchments on Ambon Island, eastern Indonesia, using catchment-specific Master Recession Curves (MRCs). Single-exponential, quadratic, and continuous two-phase formulations were evaluated using AICc, residual diagnostics, 5,000-replicate conditional bootstrap uncertainty, leave-one-observation-out sensitivity, and observational-support profiles. Recession constants ranged from 0.055046 day−¹ in Wae Ruhu (τ = 18.17 days) to 0.084950 day−¹ in Wae Tomu (τ = 11.77 days). Quadratic curvature was unsupported, while early–late changes were small (−0.512% to +0.679%), directionally inconsistent, with 95% bootstrap intervals encompassing zero. AICc favoured the single-exponential formulation, with stable ranking in four catchments and near-stability in Wae Tomu. MRC parameters therefore provide uncertainty-aware comparative descriptors for low-flow surveillance, drought preparedness, and adaptive river-basin management rather than direct proxies for groundwater-storage properties.