Duty and Delta Calculator

Duty and Delta Formula

Worked Example

A crop with a 120-day base period and a duty of 1500 ha/cumec:

1. Δ = 8.64 B / D (Δ in m, B in days, D in ha/cumec)
2. Δ = 8.64 × 120 ÷ 1500 = 0.6912 m

Duty: 1500 ha/cumec · Area irrigable D × Q: 15000 ha

GATE tip

Convert delta to the same unit as the answer: GATE often asks in cm, so 0.6912 m is 69.12 cm.

More Water Resources Engineering Calculators

• Rational Method Calculator

  Q = C i A / 360

  Q in m³/s, i in mm/h, A in ha (Q = CiA/3.6 with A in km²)

  Example: A 25 ha catchment with C = 0.6 and a design intensity of 50 mm/h: Peak runoff Q = 2.08333 m³/s.

  Open the rational method calculator →

• Hazen–Williams Calculator

  hf = 10.67 L Q^1.852 / (C^1.852 D^4.8704)

  SI units: hf, L, D in m; Q in m³/s

  Example: 100 L/s through 1 km of 300 mm pipe with C = 130: Head loss hf = 6.42347 m.

  Open the hazen–williams calculator →

Frequently asked questions

Sources

• The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .

Last reviewed: 2026-10-15. Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.