How to Build a Small Run-of-River Hydropower Station

A run-of-river hydro system consists of several interconnected components that must be carefully designed.
The intake diverts water from the river into the hydro scheme. A diversion weir raises the water level slightly to ensure adequate flow into the intake channel. Filters and trash racks remove debris that could damage the turbine. A fundamental design principle is to withdraw water from as high in the water column as possible to minimize sediment entrainment.
Water flows from the intake through the headrace channel (open or closed) to a settling basin. A coarse settling basin allows sand and heavier particles to drop out before water enters the conveyance system. Further downstream, a finer silt basin removes additional sediment.
The forebay tank acts as a buffer just before the penstock, ensuring a steady supply of water to the turbine even during minor flow fluctuations.
The penstock is the pressurized pipeline that carries water from the forebay to the turbine. It is within the penstock that the potential energy of water is converted to kinetic energy through the drop in height. Design calculations must determine the optimal diameter and thickness—balancing friction losses against material costs. Common materials include steel, PVC, and polyethylene, each with different cost and durability characteristics.
The generator converts the turbine’s mechanical energy into electricity.
The powerhouse houses the turbine, generator, control systems, and switchgear. It must be designed for safe access, maintenance, and protection from flooding.
After passing through the turbine, water is channeled via the tailrace back into the river downstream.
Construction typically proceeds in stages over one to three years, depending on project scale.
Civil Works (Year 1–2): This includes building the intake weir, excavating or constructing the headrace channel, installing the penstock (often laid along the natural terrain or buried), and constructing the powerhouse foundation and building. Civil works typically account for the largest share of capital costs—approximately 45% of total investment.
Electromechanical Installation (Year 2–3): Once civil structures are complete, the turbine, generator, control panels, and electrical equipment are installed and connected. Mechanical and electrical equipment together account for roughly 40% of capital costs.