Comparison of 6 Reference Evapotranspiration Methods For Stations Located In Humid and Sub-Humid Regions of Western Ghats

Potential evapotranspiration is an important index of hydrologic budget at different spatial scales and it is a critical variable for understanding regional biological processes. Several models have been used in computing reference evapotranspiration. This study aims at identifying a suitable alternative method to FAO-56 PM method for estimating the ET_o in Western Ghats region covering the state of Goa and Northern part of Karnataka. In the present analysis, performances of 3 radiation based methods (Makkanik, Turc and Priestly-Taylor) and 2 temperature based (FAO-56 based Hargreaves and Hamon) methods were compared with the FAO-56 PM method using the daily climatic data of 2locations namely Pajimol in Goa and Santibestwad in Karnataka for a period of 3 (2010–2012) years. ET₀ estimation of all these equations were statistically compared for daily time step. Among the ET₀ methods evaluated, estimates obtained by the TURC (temperature based) method was closest to the FAO-56 PM method at daily time step. In order to provide simpler ET₀ estimation tools, a regression equations were developed between FAO-56 PM ET₀ estimates in terms of ET₀ estimates by the simpler methods and validated for each climate. Overall, results indicated that, the simpler equations have yielded better estimates of ET₀ with smaller error for daily time step in this part of Western Ghats.