Relation Between Base, Delta, and Duty
- ‘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 in unit meters.
We know that one cumec of water is supplied 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 equations 1 and 2 we can write
⇰ (D/B)⨯ Δ = 8.64
⇰ Δ = [(8.46⨯ B)/D] Unit in meter.