Niranjan, S.Nandagiri, L.2026-02-042024ISH Journal of Hydraulic Engineering, 2024, 30, 1, pp. 85-999715010https://doi.org/10.1080/09715010.2023.2263433https://idr.nitk.ac.in/handle/123456789/21484Reference crop evapotranspiration (ET<inf>0</inf>) estimates are often unavailable at fine spatial resolutions due to the lack of dense climatic networks. The present study was taken up to develop a methodology for obtaining a gridded Penman-Monteith (PM) ET<inf>0</inf> dataset for Karnataka State, India, through spatial interpolation of estimates obtained at climate stations. Three interpolation techniques, Inverse Distance Weighted (IDW), Kriging, and Point-Based Sentinel Hospitals Area Distance (P-BSHADE), were employed to derive PM ET<inf>0</inf> estimates. Considering the historical climate records of 67 stations located in Karnataka State for the period of 2006–2016, the interpolation methodologies were evaluated using a cross-validation procedure. Results showed that the performance of IDW was better with significant error reduction at validation sites. Subsequently, the IDW algorithm was used to derive daily PM ET<inf>0</inf> values at 0.25° × 0.25° grids over the Karnataka State, India. Finally, the comparative analysis of developed PM ET<inf>0</inf> gridded data product against three global ET<inf>0</inf> products indicated the developed gridded ET<inf>0</inf> to be most accurate across different agroclimatic zones. Web links of the developed product have been created in an effort to share the data on ET<inf>0</inf>, which is a critical input in a variety of studies in earth sciences. © 2023 Indian Society for Hydraulics.CropsEvapotranspirationInverse problemsInverse distance weightedKarnatakaKrigingPenman MonteithPoint-basedPoint-based sentinel hospital area distanceReference crop evapotranspiration ETReference crop evapotranspirationsSpatial interpolationSpatial resolution