ABSTRACT
The water conveyance system that connects the intake and the forebay of a run-of-river hydropower plant is referred to as a headrace. Canals, pipes, tunnels, or other conduits, such as box culverts, are used as headraces in hydropower plants. The headrace dimensions (canal width and depth or pipe diameter) and the longitudinal slopes are sized such that the required flow can be conveyed by gravity. In case of large run-of-river hydropower plants, the headrace may also be comprised of a tunnel (referred to as a headrace tunnel). In such cases, a surge shaft is used instead of the forebay as discussed in Chapter 2. The flows along the headrace pipes or tunnels in a hydropower plant are either open-channel type (upper part of the pipe or tunnel is empty, and thus there is atmospheric pressure on the water surface) or have low pressure if flowing full.
