The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in 2011, triggered by the Tohoku earthquake and tsunami, released a substantial amount of radionuclides into the environment, including approximately 2.7 PBq of 137Cs and 200-210 TBq of tritium (3H). While extensive research has reported 137Cs concentrations across various environmental media, data on 3H levels in water resources immediately following the accident remain limited. This study examines 3H concentrations in terrestrial surface water collected from one week to 100 days post-accident. 3H concentrations ranged from 0.3 to 267.8 Bq L-1, with the highest levels exceeding typical background concentrations (0.5-2 Bq L-1) by a factor of 200. The highest 3H concentration (267.8 Bq L-1) was measured in snowmelt collected 100 km from the FDNPP one week after the accident, suggesting that snowfall effectively deposited atmospheric 3H. By one-month post-accident, all surface water samples showed 3H levels consistent with natural background concentrations, indicating rapid dispersion and dilution. No correlation was found between 137Cs and 3H concentrations, likely due to their differing deposition mechanisms and environmental behaviors. An annual effective dose estimation, based on the ingestion of the most contaminated sample (snowmelt), was 3.5 × 10-3 Sv y-1-286 times lower than the 1 mSv annual dose limit for the general public.