{"uid":"cap_wx1OZUCbkI0UwrqSTNs9D","slug":"hydrology-open-channel-calc-weir-flow-93d87ee9","name":"Hydrology & Open-Channel Calc — Weir Flow","description":"Discharge over a sharp-crested rectangular (Francis), V-notch or Cipolletti weir from head, SI or US units.","url":"https://hydrology-calc.x402tookit.com/weir-flow?utm_source=zero.xyz","method":"GET","headers":{},"bodySchema":{"type":"object","$schema":"https://json-schema.org/draft/2020-12/schema","required":["input"],"properties":{"input":{"type":"object","required":["type","method"],"properties":{"type":{"type":"string","const":"http"},"method":{"enum":["GET"],"type":"string"},"queryParams":{"type":"object","required":["type","head"],"properties":{"cd":{"type":"number","description":"Discharge coefficient Cd: rectangular then uses the (2/3) Cd sqrt(2g) form instead of Francis; V-notch default 0.585"},"head":{"type":"number","description":"Head over the crest H in metres (si) or feet (us), measured upstream of the drawdown"},"type":{"type":"string","description":"rectangular, v-notch or cipolletti"},"units":{"type":"string","description":"si (metres, m3/s; default) or us (feet, ft3/s)"},"crestLength":{"type":"number","description":"Crest length L in metres or feet (rectangular, cipolletti)"},"contractions":{"type":"integer","description":"Rectangular end contractions 0, 1 or 2 for the Francis correction (default 2)"},"notchAngleDeg":{"type":"number","description":"V-notch included angle in degrees, 10 to 120 (default 90)"}}}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object","properties":{"asOf":{"type":["null","string"]},"flow":{"type":["null","number"]},"head":{"type":["null","number"]},"type":{"type":["null","string"]},"units":{"type":["null","string"]},"source":{"type":["null","string"]},"reasons":{"type":["array","null"],"items":{"type":"string"}},"summary":{"type":["null","string"]},"verdict":{"type":["null","string"]},"degraded":{"type":["boolean","null"]},"flowUnit":{"type":["null","string"]},"warnings":{"type":["array","null"]},"disclaimer":{"type":["null","string"]},"notChecked":{"type":["array","null"],"items":{"type":"string"}},"coefficient":{"type":["null","number"]},"crestLength":{},"contractions":{},"notchAngleDeg":{"type":["null","number"]},"flowPerUnitLength":{}}}}}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.02","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.02/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.02","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.02","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_wp0RboRDYDx6t2yiAZGul","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.02","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Calculates discharge (flow rate) over a sharp-crested rectangular (Francis), V-notch, or Cipolletti weir from head measurement, in SI or US customary units.","exampleAgentPrompt":"Calculate the discharge over a 90-degree V-notch weir with a head of 0.35 metres using SI units.","exampleUseCases":[{"title":"Irrigation canal flow measurement","prompt":"I need to know how much water is flowing over a Cipolletti weir with a 1.2-metre crest length and a measured head of 0.25 metres — give me the answer in SI units (m³/s)."},{"title":"Field gauging with Francis correction","prompt":"What's the discharge over a rectangular weir that's 2.5 feet wide, head of 0.8 feet, with 2 end contractions, using US customary units? Use the standard Francis formula."},{"title":"Custom V-notch angle flow estimate","prompt":"Calculate the flow through a 60-degree V-notch weir with a head of 0.18 metres in SI units — use the default discharge coefficient."}],"resultDescription":"Returns the computed flow rate (Q) in m³/s or ft³/s, along with the weir type, head, flow unit, effective discharge coefficient, crest length, notch angle, contraction count, a plain-language summary, and any applicable warnings or disclaimers.","failureModes":["Missing required 'type' or 'head' parameters returns an error","Head value of zero or negative causes invalid computation","crestLength omitted for rectangular or Cipolletti weir returns error or null flow","notchAngleDeg outside 10–120 degree range may trigger a warning or rejection","Invalid weir type string returns an unrecognised-type error","Extremely large head values may produce physically unrealistic results with a warning"],"whenToPreferThis":"Use this endpoint when you need a fast, authoritative hydraulic calculation for standard sharp-crested weir types (rectangular/Francis, V-notch, Cipolletti) given a known upstream head, and you want SI or US unit output with optional custom discharge coefficients or Francis end-contraction corrections. Prefer this over general engineering calculators when you need weir-specific formulas with proper physical constraints and structured JSON output.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-11-02T18:30:16.662Z","isFirstParty":false,"canonicalSlug":"hydrology-open-channel-calc-weir-flow-93d87ee9"}