## Relation Between Base, Delta and Duty

Let assume,

- ‘D’ is the duty of water, unit hectares/cumec
- ‘B’ is the base period of the crop, the unit in day.
- ‘Δ’ is the total depth of water, unit meter.

We know, one cumec of water supplying continuously for **B days** to obtain a **depth of water Δ** over an area of land **D hectares**.

Hence, we can write

⇒ 1 cumec for B days gives Δ over D hectares.

⇒ 1 cumec for 1 day gives Δ over D/B hectares.

⇒ 1 cumec for 1 day(**1 cumec-day**) = **(D/B)⨯Δ** hectares-meter [Equation 1].

Now, calculate the value of **1 cumec-day** = 1**⨯**24**⨯**60**⨯**60=86400 m³.

We know that 1 hectare is equal to 10000 m², now convert 86400 m³ into a hectares-meter.

So, 1 cumec-day =86400 m³ = **8.64 hectares-meter** [Equation 2]. From equation 1 and 2 we can write

*⇰ (D/B)⨯ Δ = 8.64*

*⇰ Δ = [(8.46⨯ B)/D*] Unit in meter.

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