Discharging Sediment Downstream: The Opportunities and Challenges of Sediment Management in Sutami Reservoir, Indonesia

There is no flushing outlet facility and limited disposal sites for dredged material sediment in Sutami Reservoir. One preferable alternative to evacuate the sediment is directly downstream discharging dredged material. New research into such dredging techniques is therefore essential. This research focused on the technical opportunities and challenges of downstream discharging sediment from Sutami Reservoir. In addition, the HEC-RAS model was used to look at the impacts on the river downstream of the dam. Results showed that 400,000 m³ should be dredged at two sites (Dempok and Sumberpetung), extended the pipeline to release the slurry material downstream, and two booster pumps installed to maximize dredging productivity. There were no significant impacts on the riverbed alteration downstream of the dam. The slurry material flowed and deposited in Wlingi Dam and could be flushed periodically to avoid excess deposits. There were opportunities to save the cost of disposal area and support the replenishment of sediment. Meanwhile, the challenges were the need to monitor the environmental issues related to water quality downstream, cost investment, and water loss, which cannot re-enter the storage as conventional dredging. Finally, discharging sediment downstream was technically feasible and the best solution for sediment management in Sutami Reservoir.