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Intake site selection for RoR plant

Short answer

Select a straight, stable river reach (outer bank if on a bend) with assured dry-season level and minimal sediment. Site needs sound foundation, stable slopes, space for desander, short headrace alignment, construction access, and must avoid GLOF hazards.

What factors do you keep in mind while selecting an intake site in a RoR hydropower plant?

In a run-of-river (RoR) plant there is little or no storage, so the intake must divert the design flow reliably in all seasons while keeping sediment out. The site is chosen by considering the following factors.

Hydraulic and river factors

  1. Straight, stable reach: the river should be straight and stable for some distance upstream; if a bend is used, the intake is placed on the outer (concave) bank, where secondary currents carry bed load towards the inner bank and clear water flows towards the intake.
  2. Assured water level: the site must allow the required water level in the dry season, either naturally or with a low weir, so that design flow can always be drawn.
  3. Minimum sediment entry: avoid reaches with heavy bed load, braided channels or tributary confluences just upstream that bring large sediment.
  4. Narrow river width: a narrow section with firm banks reduces the length and cost of the weir/diversion structure.
  5. Flood levels: the intake and its gates must be safe during the design flood; high flood marks should be studied.

Geological and topographic factors

  1. Sound foundation: bedrock or a firm foundation at shallow depth for the weir and intake structures.
  2. Stable slopes: no landslides, debris flows or rock falls on the slopes around the intake.
  3. Space for structures: enough flat area for the gravel trap, settling basin and approach to the headrace.

Layout and project factors

  1. Head and alignment: the site should give the maximum gross head with the shortest and most economical headrace alignment to the forebay/surge tank.
  2. Access and construction: reasonable road access, space for construction, river diversion during construction.
  3. Environmental and social factors: downstream release (environmental flow), irrigation rights, fish migration, minimum land acquisition and resettlement.
  4. Ice, debris and glacial hazards: in Nepal, sites exposed to GLOF and debris flows should be avoided or protected.
        River bend (plan)
     ~~~~~~~~~~~~~~~~~~~\
    flow ->              \   outer bank
     ~~~~~~~~~~~~~~~~~~\  \  [INTAKE] -> headrace
                        \  \
      inner bank (bed    \  \
      load deposits)      \  \

✓ Answer checked by Claude Opus 5.5 (high effort)

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