Stable isotopic composition (δ²H, δ¹⁸O) of river water, groundwater, and paddy water in the Mun River catchment, northeast Thailand, were determined to investigate the hydrological processes and the impacts of natural and anthropogenic activities on the water cycle. Quantities of δ²H (−93.9 to −25.4‰) and δ¹⁸O (−12.24 to −2.22‰) in river water in the wet season follow the trend: upper reaches > middle reaches ≈ lower reaches. Trends for δ²H (−52.3 to −22.0‰) and δ¹⁸O (−6.37 to −1.36‰) in the dry season are: upper reaches ≈ middle reaches > lower reaches. In the dry season, groundwater (δ²H: −57.5 to −34.6‰, δ¹⁸O: −8.24 to −4.40‰) shows a lighter isotopic composition, and paddy water (δ²H: −18.2‰, δ¹⁸O: −0.72‰) shows the highest isotopic composition. Spatial variation of δ¹⁸O and deuterium excess suggests that groundwater exchanges with surface water frequently. Rainfall and river water recharge groundwater in the wet season, and groundwater flows back to the river in the dry season, especially in the middle reaches. This process is most likely related to impoundment of the rivers by large dams. On the other hand, the lowest values of stable isotopes of river water are coincident with the extreme flooding that was produced by Tropical Storm Sonca in July 2017. This study contributes to a better understanding of hydrological processes in the Mun River catchment and provides a perspective on the application of stable isotopes to other large tropical monsoon catchments around the world.

稳定同位素组成（δ ² H，δ ¹⁸ O）河水，地下水和稻田水在门河流域，泰国东北部，确定调查水文过程和的自然和人为活动对水循环的影响。δ的数量² H（-93.9至-25.4‰）和δ ¹⁸在潮湿季节O（-12.24至-2.22‰）河水中跟随趋势：上游>中游≈下游。对于δ趋势² H（-52.3 -22.0至‰）和δ ¹⁸ O（-6.37 -1.36至‰）在干燥的季节是：上游≈中游>下游。在干燥的季节，地下水（δ ² H：-57.5至-34.6‰，δ ¹⁸○：-8.24至-4.40‰）示出了较轻的同位素组成，和稻田水（δ ² H：-18.2‰，δ ¹⁸ ○：-0.72‰）显示了最高的同位素组成。δ的空间变异¹⁸O和氘过量表明地下水经常与地表水交换。雨季降雨和河水补给地下水，而在旱季，特别是在中游地区，地下水流回河中。这个过程很可能与大型水坝的蓄水有关。另一方面，河水的稳定同位素的最低值与热带风暴桑卡在2017年7月发生的极端洪水相吻合。这项研究有助于更好地了解门河流域的水文过程，并提供一个视角稳定同位素在世界其他大型热带季风流域的应用