Seasonal and Spatial Characteristics of Suspended Sediment Load and their Controlling Factors in the Upper Indus River Basin, Pakistan

Abstract

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 stationsaccounted for 34.0 at Kachura, 86.7 at Bunji Bridge, 75.7 at Shatial and 57.7 (Mt) at Besham Qila, 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 Shatial, 76% at Besham Qila,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. Results indicate that serious soil erosion occurred mainly during three months (June, July and August). It is therefore, strongly recommended to reduce soil loss and launch soil conservating activities such as: toenhance vegetation cover,forestation and, professional development works in the area, which could play an effective role to extend the lifeline of proposed water resource projects, especially Tarbella (the largest reservoir), andthe Diamer Bhasha (an under-construction dam in the region).