MODELlING HYDROLOGIC PROCESSES DISTRIBUTION IN A TROPICAL FOREST WATERSHED in the PHILIPPINES

Hydrologic modelling has become an indispensable tool and cost-effective process in understanding the movement of water loss in the Molawin rainforest watershed, Philippines. The study aimed to optimise the use of a lumped BROOK90 model and simulate the hydrologic processes distribution in a given watershed. The rating curve model was developed as a basis for hydrologic modelling. The model was calibrated at catchment scale to avoid subjectivity of various variable parameters by considering the topography, morphology, climate, soil and canopy characteristics. Five years of streamflow discharge measurements were considered for the model sensitivity analysis, calibration and validation. Results showed a good agreement between observed and simulated streamflows during calibration (r = 0.87 and E = 0.87) and validation (r = 0.84 and E = 0.81) periods. As a consequence, the major hydrologic processes distribution accounted for 41% of the precipitation that turned into evaporation, while 49% became streamflow and 10% remained in deep seepage loss. Overall, the distribution of hydrologic components is primarily reflected during pronounced seasonal variations and fluctuating patterns in precipitation.