Applicability of the Climate Hazards Group Infrared Precipitation with Stations as Rainfall Input for SWAT Watershed Modeling

This study assessed the applicability of Climate Hazards Group Infrared Precipitation with Stations (CHIRPS) as rainfall input in watershed modeling using the Soil and Water Assessment Tool (SWAT). The CHIRPS and ground-based rainfall data were used to calibrate and validate the SWAT model in four selected watersheds from each of the four Climate Types in the Philippines. The SWAT performed adequately with CHIRPS across sites during calibration (R-2 > 0.74, NSE > 0.71, PBIAS between -6.92 and +12.92, and RSR < 0.54) and validation (R-2 > 0.68, NSE > 0.67, PBIAS between -4.24 to 13.13, and RSR < 0.57). The SWAT models of small watersheds with rainfall inputs from both weather stations and CHIRPS exhibited almost similar results. The ground-based rainfall from one station was not enough to achieve reliable SWAT simulations of streamflow in relatively large watersheds. The CHIRPS proved to be an adequate rainfall source for watershed modeling and can be used as an alternative or supplementary SWAT input in small and large watersheds. This study may serve as a useful reference for water resources managers, policy, and decision-makers in dealing with sparse rainfall monitoring network that is of utmost importance in water resources planning.