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# Relation between Base Period, Duty and Delta?

## Base Period:

The time on which crop is watered, the time from first watering to last watering of crop by which the crop grows.

The base period is in days and denoted by B

The base period is less than crop period

Crop period is whole time on a crop

Base period is only watering period in which crop is irrigated

Note: Base period is different than Crop Period, because crop period is total time taken by any crop upto harvesting but base period is only watering period.

## Duty:

Duty is the area of land irrigated in one cumec of watering.

It is calculated in hectare

## Delta:

Delta is the depth of water required for a crop to fully grow in entire season

Delta is calculated in centimetre or metre and denoted by

## Relation Between Duty, Delta and Base period

Relationship clarify that the volume of water supplied to crop in its base period and volume of water necessary to matures an area of D hectare.

Let

D = Duty in hectare/cumec

B = Base period in days

Δ  = Delta in metre

The volume of water(V) supplied to a crop during base period(B)

V1 = Bx24x60x60

V1 = 86400 B m3

suppose that we supply V volume of water, and the one cubic metre of water per second for a base period matures an area of D hectare.

Volume = matures 1 hectare of depth

V2 = 10000 D sq mtr x Δ

So equant the volume of supply and volume of maturity crop

V1 = V2

86400 B = 10000 D x Δ

Duty of water in hectare/cumec is calculated by 8.64 base period divided by depth of Δ

Example 1

A canal was designed to supply irrigation needs of 1200 ha of land growing rice of 140 days base period and having a delta of 134 cm. IF the canal waters are used to irrigate wheat of base period 120 days and having a delta of 52 cm the area that can be irrigated is ?

• 2651 ha
• 543 ha
• 3608 ha
• 2592 ha

Solution:  use duty, delta and base period formula

### Case 1:

Base Period = 140 Days

Delta = 1.34 m

So Duty is equal to = 8.64X140/1.34 ha/cumec

D = 902.68 ha/cumec

We have 1200 ha of land,

Total Land = Total water of canal X Duty

so total water in canal is = 1200/902.68 = 1.33 cumec

Case 2:

Base Period = 120 Days

Delta = 0.52 m

So Duty is equal to 8.64×120/0.52

D = 1993.85 ha/cumec

We have 1.33 cumec of water in canal (by case 1) so the land area is ?

Land = total water of canal X Duty

So Land would be irrigated is = 1.33 X 1993.85 = 2651.82 ha

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