The water isotopic composition (δ¹⁸O and δ²H) of humid tropical mountain belts is influenced by the limited isotopic elevation effect due to the narrow temperature gradient, high relative humidity, and the moisture feedback processes. The Western Ghats mountain forest ecosystem, recognized as a biological hotspot, contributes significantly to characterizing the hydrological and weather patterns over its windward and leeward sides. The Indian Summer Monsoon southwesterly winds advancing towards the Indian subcontinent through the Arabian Sea between June to September are obstructed by this mountain belt and get orographically uplifted, producing heavy rainfall. The present study intends to improve understanding of the variation of precipitation isotopic composition along multiple stations located at different elevations of the heavily regulated Periyar river basin (PRB), southern Western Ghats, and a coastal station (TRV). The δ¹⁸O variation with elevation across PRB reveals an abrupt depletion at the highland station and a pseudo-elevation effect due to the supply of evaporated local moisture from reservoirs and lakes. The contribution of recycled precipitation estimated using back trajectories suggests a maximum of 8.5% of locally recycled rainfall over midland station towards the September month, the daily contribution reaching a maximum of 50.7%. Though this approach did not show any signatures of moisture recycling in the highland station, the surface water (reservoirs and lakes) lc-excess (line-conditioned excess), and the d-excess (deuterium excess) values of precipitation suggest the higher rates of evaporation from large water bodies and their successive role in generating local rainfall. Statistically significant amount effects visible only along coastal stations with lower rates of precipitation and higher temperature indicate that precipitation along the Ghats region (midland and highland) is significantly controlled by orographic uplift of air moisture and the contribution from locally recycled moisture. This is further supported by the significant correlation of δ¹⁸O with regional convective processes along the Arabian Sea till midland station and further decrease towards the highland. The present study provides important information on the moisture feedback mechanism in the Western Ghats and the factors controlling the isotopic signatures over the region.

水同位素组成（δ ¹⁸ O 和 δ ²H) 由于温度梯度窄、相对湿度高和水分反馈过程，潮湿热带山带受有限的同位素高程效应的影响。被公认为生物热点的西高止山森林生态系统对表征其迎风侧和背风侧的水文和天气模式做出了重大贡献。6 月至 9 月间，印度夏季风通过阿拉伯海向印度次大陆推进的西南风被该山带阻挡并在地形上抬升，产生强降雨。本研究旨在提高对位于受到严格管制的佩里亚尔河流域 (PRB) 不同海拔的多个站点降水同位素组成变化的了解，西高止山脉南部和一个沿海车站 (TRV)。δ¹⁸整个 PRB 随海拔变化的 O 变化表明高地站的突然枯竭和由于水库和湖泊蒸发的局部水分供应而产生的假高程效应。使用回溯轨迹估算的循环降水贡献表明，到 9 月份，米德兰站局部循环降水的最大贡献率为 8.5%，每日贡献最大为 50.7%。虽然这种方法没有显示出高地站水分循环的任何特征，但地表水（水库和湖泊）lc-excess（线路条件过剩）和 d-excess（氘过剩）降水值表明较高的速率大水体的蒸发及其在产生局部降雨中的连续作用。仅在降水率较低和温度较高的沿海站点可见的统计显着量效应表明，沿高止山脉（中部和高地）的降水显着受空气湿度的地形抬升和局部再循环水分的贡献控制。δ 的显着相关性进一步支持了这一点¹⁸ O 伴随着沿阿拉伯海的区域对流过程，直到中部站，然后向高地进一步减弱。本研究提供了有关西高止山脉水分反馈机制和控制该地区同位素特征的因素的重要信息。