Spatial Modeling of Evapotranspiration for Efficient Water Management at Regional Scale

The meteorological data on maximum and minimum temperature, maximum and minimum humidity, wind speed and sunshine hours were collected from IMD-AWS as open source data for 373 stations for 50^th and 20^th meteorological week of 2011 and 2012, respectively. The data of 353 stations were used to develop water balance model and 20 stations were used for validation and testing of the model. Data were used to compute potential evapotranspiration using Penman-Monteith method. These locations with their respective latitude, longitude and elevation were brought under GIS environment for spatial database management. Separate layer of water deficit/surplus database was generated using derived evapotranspiration and rainfall data. The derived water deficit/surplus data was further interpolated into 2 km x 2 km grid using RBF (radial basis function) interpolation algorithm to produce spatial water balance model for the given week. The developed methodology was tested for 20 different locations. It was found that the model overestimated lower values and underestimated higher values. Overall, for all 20 locations, the model estimated 7.6% higher PET with average of 18.55 mm for the week under consideration (50^th and 20^th meteorological week of year 2011 and 2012, respectively). The range of the model prediction was found to be 26.86 mm as compared to observed value of 34.80 mm. The standard error was computed as 1.91 mm for estimates while it was 2.19 mm for observed.