Common RoR intakes in Nepal; site selection

Intakes commonly used in RoR projects in Nepal

1. Side intake: an opening in the river bank, with a trash rack and gate, built at the side of the weir and undersluice. It is the most common type in Nepal because the river carries a large bed load and the flow can be diverted with simple structures.
2. Bottom (Tyrolean / drop) intake: a trench with a rack across the river bed in steep, boulder-carrying streams; water drops through the bars into a collection chamber (used in small hydropower and micro-hydro projects in the hills).
3. Frontal intake: an opening at the front of the weir facing the flow (less common because it takes much bed load).

Factors for selecting the intake location

• Outer (concave) bank of a stable river bend, where the secondary current moves bed load away from the intake; or a straight stable reach.
• Stable river reach and good foundation: rock or firm soil; no active landslide or erosion.
• Sufficient head and level to give gravity flow to the settling basin and headrace without long canals.
• Away from sediment deposition zones, confluences of tributaries and high debris areas.
• Good access for construction, operation and maintenance.
• Cheap river training and weir construction: a narrow section where the weir is short, and enough space for the gravel trap and settling basin close by.
• Flood safety: high flood level, minimal flood damage to the headworks and powerhouse.
• Environmental and social: minimum effect on existing water users, fish and forest.