Evapotranspiration rates from measured meteorological parameters and quantification of tritium flux at the Kaiga site

The evapotranspiration(ET) rate at the Kaiga Nuclear Power Plant (NPP) site, India, was calculated for the year 2023 using four empirical methods: the FAO-56 Penman–Monteith theory, Turc, Makkink, and Priestley-Taylor equations. The resulting annual average ET rates were estimated as 1.45 mm.d⁻¹, 1.89 mm.d⁻¹, 3.2 mm.d⁻¹, and 4.38 mm.d⁻¹ respectively. Tritium released to the atmosphere via the NPP stack mixes with ambient air moisture and subsequently exchanges with water reservoirs in soil and vegetation. The tritium evapotranspiration flux was computed by combining the modeled ET rates with the atmospheric tritium concentration. Across the four models, the annual average tritium evapotranspiration flux in the vicinity of the Kaiga NPP during 2023 ranged from 0.32 to 0.94 mBq.m⁻².s⁻¹. This study successfully generated crucial site-specific ET and tritium flux data, which are necessary input parameters for models predicting the environmental transfer and distribution of tritium.