Submergence Check Tool (Multi‑Method)

Inputs

Unit system

Gravity, g (m/s²) Default is standard gravity. Use local gravity only if needed.

Compute g from latitude & elevation (optional)

Design discharge, Q (m³/s)

No. of openings, n

Opening shape

Opening width, b (m)

Opening depth/height, d (m)

D for D‑based methods (rectangular only) Used only where a method requires a single characteristic size D. Deq: – Dh: –

How d, Deq and Dh are used in this tool

Rectangular opening: Area per opening A = b × d (used for velocity). For methods that require a single characteristic size D, you may choose:

d = opening depth/height
Deq = √(4A/π) (equal-area equivalent diameter)
Dh = 4A/P, where P = 2(b + d) (hydraulic diameter)

Circular opening: A = πD²/4 and D is the actual diameter.

Note: velocity is always computed from the true area; only D‑based criteria use the selected D option.

Intake type (for Gordon k)

Sill / invert level (masl) Used to auto-fill Crown & Centerline from Sill + opening height.

Crown elevation (ref.) (masl)

Centerline elevation (ref.) (masl)

Minimum Operating Level (MOL) (masl)

Tip: Some methods define submergence above crown, others above centerline. This tool reports both unit systems; calculations are performed internally in SI.

Summary

Area, A

–

Approach velocity, v

–

Gravity, g

–

Governing minimum WL: – Governing method(s): – Check vs MOL: –

Governing WL is the maximum required minimum water level among the selected methods.

Governing ref. line: –

Opening shape: –

D used for D‑based methods: –

Method comparison

Method	Include?	Submergence, S	Ref. line	Min. WL

Notes:

If multiple methods give the same governing WL (tie), all of those rows will be highlighted.
Prosser (1970) is expressed as S = 1.5D. This tool reports required submergence above the intake centreline. For non‑circular openings, D‑based methods use the selected equivalent diameter (Deq or Dh), or the opening depth/height (d). Prosser may be deselected where not applicable.

Submergence definition sketch

Figure: Typical definition of submergence S, opening depth/diameter D and approach velocity.

References (from the attached sheets)

Gordon (1970) — in ASCE “Guidelines for Design of Intakes for Hydroelectric Plants”.
Prosser (1970) is expressed as S = 1.5D. This tool reports required submergence above the intake centreline. For non‑circular openings, D‑based methods use the selected equivalent diameter (Deq or Dh), or the opening depth/height (d). Prosser may be deselected where not applicable.
Pennino & Hecker (1980) — submergence relation.
Gulliver & Rindel (1986) — submergence relation.
IS 9761:1995 — criteria using Froude number at intake.
ITDG Manual — micro/mini‑hydro intake guideline using velocity head.