Hydrological Reconstruction in Obrajillo with SWAT And Gridded Climate Data

In high Andean regions such as the Obrajillo watershed, water resource management is limited by the scarcity of reliable meteorological stations and short hydrological records. This lack of information hinders infrastructure design and the assessment of risks associated with extreme events. To address this issue, the SWAT hydrological model was implemented through ArcGIS (ArcSWAT) and calibrated using SWAT-CUP, incorporating gridded climate products such as PISCOp v2.1, RAIN4PE, and CHIRPS. Calibration was performed for the period 1998–2008 and validation for 2009–2014, yielding favorable results: PISCOp achieved an R² of 0.80, NSE of 0.70, and a PBIAS of 23.16. This enabled the reconstruction of daily streamflows from 1980 to 2014. Additionally, maximum flows associated with different return periods were estimated—an essential input for water infrastructure planning and risk management. For this purpose, empirical formulas such as Fuller’s and its adjusted variant were applied to estimate peak instantaneous discharge based on the watershed area and base flow. The adjusted expression accounts for the rapid runoff concentration in smaller catchments, which tend to produce more intense peak events. The implemented methodology proved effective in compensating for hydrological data gaps and supporting decision-making in contexts of high climatic variability and limited instrumentation.