Learn:Methods of Determining duty of water,Duty by Inductive Method,Critical Growth Period Basis

# METHODS OF DETERMINING DUTY OF WATER

The duty of water can be found,out by any of the following three methods

1. Inductive method.
2. Critical growth period basis

1. Duty by Inductive Method.

• This method is based mostly on past experiments and experiences.
• Various states have developed standard duty tables depending upon.
• The methods of irrigation adopted by them.
• Methods adopted by various states to determine discharge in the channels to meet the crop requirements vary.

Following are the methods mostly adopted:

(A) In this method, the percentages of areas under different crops water allowance for the entire C.C.A. for a particular channel fixed.

• An example of this method may be 0.17 cumec per 1000 hectares.
• This method of fixing the duty.

(B) the method outlet discharge factors for different crops of the region  standardized.

• Based on outlet discharge factor, and crops  grown in each.
• season discharges required for Kharif and Rabi seasons separately worked out.
• The channel is design for the maximum of the two discharges.

(c) In this method, based on the standard duties of various

• crops and area under cultivation in each crop, month-wise required discharges are worked out.
• The channel is design to meet the maximum requirements of discharge, required in a month.

Example 3.1. Determine the maximum discharge at the outlet of a distributary having following crop areas and duties of water.

Solution. Discharges required in cumec for maturing different crops are as follows.

The discharges required during different seasons are as follows:

• It is seen from this table that maximum discharge of 10 cumecs is required during Kharif.
• Hence distributary should be design for this discharge.

2. Critical Growth Period Basis.

• This method is based on the concept that crops require different quantities of water at various stages of their growth.
• The water requirements of all the crops are usually maximum during initial growth and then at flowering period.
• It is minimum during maturing period.
• This is because Kor watering itself requires more water, and more so this watering has to be suppli to the crop during the limit Kor period.
• The Kor periods for wheat.