Seasonal and spatial characteristics of suspended sediment load and their controlling factors in the Upper Indus River Basin, Pakistan

Understanding the seasonal and spatial characteristics of suspended sediment load is extremely important for efficient water resource management. The characteristics of suspended sediment load reflect the soil erosion, transport, and deposition. The upper Indus basin is a single source of fresh water and hydropower generation for the surroundings and downstream areas with a population of millions approximately. Simultaneously, the water resources in this area are badly affected by the sedimentation. Therefore, the focus of this study is to evaluate the seasonal variation and spatial distribution of suspended sediment load and figure out their controlling factors by using hydrometeorological data series collected from WAPDA and PMD. Annual sediment load at four mainstream stations accounted for 34.0 at Kachura, 86.7 at Bunji Bridge, 75.7 at Shatial and 57.7 (Mt) at Besham, respectively. The high sediment loads were observed during the summer season, accounting for 77.4% at Kachura, 85.6% at Bunji Bridge, 73.7% at Shatialand 76% at Beshamand 92.9% at Shyok, 69.1% at Hunza, 47.9% at Gilgit and 57.0% at Astore tributary respectively. Conclusively, contrasting suspended sediment load variability was observed throughout the study area. The high values of sediment loads were observed during the summer season, especially occurred during June, July and August. This indicates that serious soil erosion occurred during these three months in the area. It is therefore, strongly recommended to reduce soil loss and launch soil conservating activities, forestation and professional development work in the area, which could play an effective role to extend the lifeline of proposed water resource projects, especially the Diamer Bhasha (an under-construction dam in the region).