Analyzing sedimentation patterns in the Naumure Multipurpose Project (NMP) reservoir using 1D HEC-RAS modeling

Area of Science:

• Hydraulic Engineering
• Environmental Engineering
• Sediment Transport Modeling

Background:

• Nepal's rivers, including the West Rapti, carry substantial sediment loads.
• Reservoir sedimentation significantly reduces the operational lifespan and effectiveness of multipurpose projects.
• This impacts flood control, hydroelectricity generation, economic feasibility, and long-term sustainability.

Purpose of the Study:

• To analyze the projected sediment deposition patterns in the Naumure Multipurpose Project (NMP) reservoir.
• To assess the impact of sedimentation on the NMP reservoir's storage capacity over 50 years.
• To understand the implications for the project's operational viability.

Main Methods:

• Utilized a 1D HEC-RAS model to simulate reservoir sedimentation.
• Employed Yang's equation for sediment transport, Active layer for bed sorting, and Toffaleti for fall velocity.
• Simulations were conducted for 10, 20, 30, 40, and 50 years of operation.

Main Results:

• Significant delta deposition was observed in both the Jhimruk and Madi river inflows.
• Sediment deposition depth in the Jhimruk reached up to 49m, and in the Madi up to 75m after 50 years.
• Reservoir storage capacity depletion reached 25.65% by year 50, with headcutting observed between years 20-30.

Conclusions:

• Sedimentation poses a substantial threat to the NMP reservoir's long-term functionality.
• Proactive sediment management strategies are crucial for ensuring the project's sustainability.
• The study provides critical data for informed decision-making regarding the NMP.