The Sutlej River basin of the western Himalaya (study area), owing to its unique geographical disposition, receives precipitation from both the Indian summer monsoon (ISM) and the Westerlies. The characteristic timing and intensity of the ISM and Westerlies, leaves a distinct footprint on the sediment load of the River. Analysis with the last forty years data, shows an increasing trend for temperature. While for precipitation during the same period, the Spiti watershed on the west has highest monthly accumulated precipitation with long term declining trend, in contrast to the other areas where an increasing trend has been observed. Thus, to probe the hydrological variability and the seasonal attributes, governed by the Westerlies and ISM in the study area, we analyzed precipitation, temperature, snow cover area (in $\%$), discharge, suspended sediment concentration (SSC) and suspended sediment load (SSL) for the period $2004$ - $2008.$ To accomplish the task, we used the available data of five hydrological stations located in the study area. Inter-annual shift in peak discharge during the monsoon period is controlled by the variation in precipitation, snow melt, glacier melt and temperature. Besides seasonal variability has been observed in generation of the sediments and its delivery to the river. Our analysis indicates, dominance of the Westerlies footprints in the hydrological parameters of the Spiti region, towards western part of the study area. While, it is observed that the hydrology of the Khab towards eastern part of the study area shows dominance of ISM. Further downstream, the hydrology of Nathpa station also shows dominance of ISM. It also emerged out that the snowmelt contribution to the River flow is mostly during the initial part, at the onset of the monsoon, while for rest and major part of the summer monsoon season, the River flow is augmented by the precipitation, glacial melt and some snow melt. We observed, that the SSC increases exponentially in response to increase in temperature and correlates positively with River discharge. The average daily SSL in the summer monsoon is many times more than that in the winter monsoon. The downstream decrease in steepness of the sediment rating curve is attributed to either a change in the River-sediment dynamics or on account of the anthropogenic forcing. The top $1\%$ of the extreme summer monsoon events (only $4$ events) in our study area contribute up to $45\%$ of SSL to the total sediment load budget. It has also been observed that the River-sediment dynamics in the upstream catchments are more vulnerable and sensitive to the extreme events in comparison to the downstream catchments. The present study for the first time gives a holistic insight in to the complex dynamics of the hydrological processes operational in the study area. The research findings would be crucial for managing the water resources of the region and the linked water and food security.

喜马拉雅西部（研究区）的 Sutlej 河流域，由于其独特的地理配置，接收来自印度夏季风 (ISM) 和西风带的降水。ISM 和西风带的特征时间和强度，在河流的泥沙负荷上留下了明显的足迹。对过去四十年的数据进行分析，显示温度呈上升趋势。而同期降水量方面，西部斯皮提流域月累积降水量最高，且呈长期下降趋势，其他地区则呈上升趋势。因此，为了探讨研究区受西风带和 ISM 控制的水文变异和季节属性，我们分析了降水、温度、积雪面积（在$\%$)、该期间的排放量、悬浮泥沙浓度 (SSC) 和悬浮泥沙负荷 (SSL) $\mathrm{2004年}$ —— $\mathrm{2008年}.$为了完成这项任务，我们使用了位于研究区的五个水文站的可用数据。季风期间峰值流量的年际变化受降水、雪融化、冰川融化和温度变化的控制。除了在沉积物的产生及其向河流中的输送方面观察到季节性变化。我们的分析表明，西风足迹在斯皮蒂地区的水文参数中占主导地位，朝向研究区的西部。同时，观察到研究区东部的 Khab 的水文显示 ISM 占主导地位。再往下游，Nathpa 站的水文也显示出 ISM 的主导地位。还发现融雪对河流流量的贡献主要发生在季风开始时的初期，而在休息和夏季季风季节的大部分时间，河流流量因降水、冰川融化和一些雪融化而增加。我们观察到，SSC 随温度升高呈指数增加，并与河流流量呈正相关。夏季季风的平均每日 SSL 是冬季季风的数倍。下游沉积物等级曲线陡度的降低归因于河流沉积物动力学的变化或人为强迫。顶端 夏季季风的平均每日 SSL 是冬季季风的数倍。下游沉积物等级曲线陡度的降低归因于河流沉积物动力学的变化或人为强迫。顶端 夏季季风的平均每日 SSL 是冬季季风的数倍。下游沉积物等级曲线陡度的降低归因于河流沉积物动力学的变化或人为强迫。顶端$1\%$ 极端夏季季风事件（仅 $4$ 事件）在我们研究领域的贡献高达 $45\%$SSL 对总沉积物负荷预算的影响。还观察到，与下游流域相比，上游流域的河流沉积物动态对极端事件更加脆弱和敏感。本研究首次全面了解研究区域内运行的水文过程的复杂动态。研究结果对于管理该地区的水资源以及相关的水和粮食安全至关重要。