Navigating reservoir sedimentation through hydro-suction

Abstract

Reservoir sedimentation is a significant global challenge, including in India, for the sustainable management of vital hydraulic structures, impacting storage capacity, water demands, and ecological balances. The United Nations University - Institute on Water Environment and Health (UNU-INWEH) study has revealed that out of 47,403 large dams in 150 countries, the initial global storage of 6,316 billion cubic meters (BCM) is projected to decline to 4,665 BCM by 2050. This loss of 1,650 BCM is equivalent to the annual water use of India, China, Indonesia, France, and Canada combined. The report highlights the alarming decline in storage capacity across the globe. The current study delves into the effectiveness of hydro-suction as a solution for reservoir desilting, exploring its applications through success stories and experimental investigations. Hydro-suction is a proven efficient method for sediment removal, avoiding disruptions to ecosystems and structures. This method utilizes suction forces to remove the sediment from the bed surface without interfering with the processing of the connecting structures such as irrigation canals and hydropower plants. The study presents successful global applications of hydro-suction in desilting reservoirs, showcasing its effectiveness in real-world cases. The global success stories highlight diverse implementations and positive outcomes of the hydro-suction sediment removal method. In Djidiouia Reservoir, hydro-suction effectively removed 1.4×106 m³ of silt and clay over two years, addressing rapid silting. Rioumajou Dam's hydro-suction system prevented sediment buildup, discharging 1 m³/s and paying off installation costs within a year. Tianjiawan Reservoir's hydro-suction system reclaimed storage capacity, removing 0.32×106 m³ of sediment with a mean concentration of 15.6%. In Xiao Hua-shan Reservoir, sediment removal enhanced reservoir storage, hydropower generation, and downstream cropland topsoil quality. The Geolidro technique in Alpine reservoirs effectively removed over 5×106 m³ of sediment in a span of 20 years. Further case studies include Alonia Lake's cost-effective sediment removal, California Reservoir's proposed hydro-suction system, Billings Lake's prevention of hydropower loss, and Palagnedra Reservoir's successful sediment removal despite limitations. Along with the success stories, the current study also presents the interpretations from the experimental study done at the Indian Institute of Technology (IIT) Roorkee. The study systematically studied the area of influence of the suction force generated below the suction pipe during the hydro-suction by strategically changing the effective parameters, including suction pipe diameter, suction inlet height, suction discharge, and sediment median size, studied. A total of 252 experimental runs provide insights into the diameter and depth of influence below the suction pipe during hydro-suction. The analysis of diameter and depth of influence during hydro-suction experiments emphasizes the significance of suction inlet height and suction discharge. A Whisker's plot suggests an anticipated range of 2D to 3.5D for the diameter of influence and 0.5D to 0.8D for the depth of influence during hydro-suction sediment removal. The case histories demonstrate the adaptability of hydro-suction in addressing sedimentation challenges across different regions. The experimental investigation would help plan and design the system for area-specific sedimentation removal. Hydro-suction can be a viable and environmentally friendly strategy for managing reservoir sedimentation.