Verified calculation capability

Parshall flume Calculation Capability

USBR 1–8 ft Parshall free-flow Q from throat W and gage Ha, n=1.522 W_ft^{0.026}. Not thin-plate weir, not broad-crested weir, not Manning, not Q=Av, not orifice. · Physics · Fluid

Capability ID physics.fluid.parshall_flume · version 1.0.0

Open calculator REST API MCP Evidence Evidence JSON Review policy

Model

USBR free flow

USBR free flow: Q_cfs = 4 W_ft Ha_ft^n
Exponent: n = 1.522 W_ft^{0.026}

Solve modes: flow · head

Inputs / Outputs

Canonical symbols for this capability. Agent schemas remain the contract.

Symbol	Quantity	Unit	Role
`W`	Throat width in m. Required. Envelope [0.3048, 2.4384]. Alternatives: W_m, throat, throat_width. Do not send weir b or L.	—	input / output
`Ha`	Specified-gage upstream head in m. Required for flow. Envelope [0.03048, 1.6764]. Alternatives: H_a, h_a, Ha_m. Do not send weir H.	—	input / output
`Q`	Volume flow in m³/s. Required for head invert. Alternatives: flow, Q_m3_s.	—	input / output
`n`	amount of substance	—	output
`model`	—	—	output

Assumptions / Validity

Declared scope for this capability. Do not use it outside this domain.

Assumptions

USBR 1–8 ft Parshall free flow: Q_cfs = 4 W_ft Ha_ft^n, n=1.522 W_ft^{0.026}; SI W, Ha, Q; n is reported, not an input
Ha is the specified-gage upstream head, not weir crest head H; W∈[0.3048 m, 2.4384 m]; Ha∈[0.03048 m, 1.6764 m]; free nappe only
Not thin-plate (2/3) C_d L √(2g) H^{3/2}, not broad-crested (2/3)^{3/2} b √g H^{3/2}, not Manning n, not Q=Av, not orifice, not submerged Hb

Not supported

thin-plate weir
broad-crested weir
Manning n
Q=Av
orifice
1–9 in Parshall C tables
submerged Hb/Ha
SANIIRI

Example

One numerical check. The calculator page holds worked steps and FAQ.

W=0.3048 Ha=0.3048 → Q≈0.11327

Open this example in the calculator

Trust

Review-policy: engine tested — automated tests, sources, version lock, and evidence published. Supplemental to CVP; not Domain Expert Review. See CVP and Review policy.

Tier: Engine tested — catalog token engine_tested
Calculation version: 1.0.0
Evidence tests: 5/5 calculation tests · golden 0/0 · boundary 0/0 · property 5/5
Engine tested: Yes
Source checked: Yes
Supplemental domain review: Not performed
Named expert review: Not performed
Version lock: Supported (409 VERSION_MISMATCH)
Artifact consistency: Build verified · 1.0.0 (workspace artifacts agree)

Production attestation: Embedded snapshot: STALE · Last attested schema matched 1.0.0 snapshot / local build · Semantic contract ✓ · Last attestation PASS · current evidence changed · re-attestation required · Public/cache ✓ · Origin ✓ · Live production status PASS (0 stale; 164 CURRENT) @ 2026-09-18T02:44:05.986Z
Semantic contract: PASS
Evidence attested at: 2026-09-18T02:44:05.231Z
Last production check: 2026-09-18T02:44:05.231Z
Public / cache: PASS
Origin: PASS

Call this capability

Human page, REST, and MCP share the same engine and calculation_version. Build verified hashes workspace artifacts only. After deploy, attest:production GETs canonical URLs twice — the public/cached view an Agent actually hits, and origin — including every /capabilities/{id} HTML page. Public Capability HTML version must match catalog before production attestation passes. Live Trust rows above fetch /.well-known/calculatorx-production-attestation.json and the output schema const. Build hashes: release integrity. That proves currently published page / engine / schema / evidence / MCP agree — not that a historical version is independently immutable. Production surface contract 1/1.

Tool id: parshall-flume
Engine: parshall-flume
REST: POST /api/v1/calc/parshall-flume
MCP: execute_calculation with capability_id: "physics.fluid.parshall_flume"
Agent input schema: Canonical (MCP / Agent)
Output schema: JSON Schema (latest)
Versioned input schema: Immutable pin (1.0.0)
Versioned output schema: Immutable pin (1.0.0)

References

Human-readable sources plus CVP reference evidence classes.

Sources

ISO 9826 — Measurement of liquid flow in open channels — Parshall and SANIIRI flumes — Parshall flume
USBR Water Measurement Manual — Parshall flumes, 1–8 ft
ISO 80000-4 — Mechanics — Volume flow rate

Try with an agent

Inspect this capability via same-origin MCP, then call execute_calculation.

curl -sS -X POST 'https://www.calculatorx.com/mcp' \
  -H 'Content-Type: application/json' \
  -H 'MCP-Protocol-Version: 2026-07-28' \
  -H 'Mcp-Method: tools/call' \
  -H 'Mcp-Name: inspect_capability' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"inspect_capability","arguments":{"capability_id":"physics.fluid.parshall_flume"}}}'

Inspect the trust tier and required assurance level before execution. Pin calculation_version (1.0.0) when reproducibility matters. Full protocol notes: MCP docs.