Relationship of delta, duty & base period

# DUTY: 

    The area of land that can be irrigated with a unit volume of water supplied is called duty. It is denoted by D.

# DELTA: 

 The depth of water required to raise a crop over a unit area is called delta. It is denoted by Δ.

# BASE PERIOD:

   The time between the first watering of a crop at the time of its sowing to its last watering before harvesting is called the base period. It is denoted by B.

#  RELATIONSHIP AMONG DUTY, DELTA AND BASE PERIOD.

   

Let us consider a crop having base period B days. Assume that 1 cumec of water is supplied to this crop for B days to provide delta Δ  m depth of water.

           Now the volume of water supplied by unit discharge  to this crop during B days is given by:

                      V=Q (m³/s)*B (days)

                      V= 1*24*60*60*B m³

                      V=8.64*10000 m³                   …………………(1)

      Also, the volume of water applied to the field can be calculated as:

                       V=Area of land irrigates by unit discharge*depth of water applied

                       V=D(ham)*Δ (m)

                       V=D *A*10000(m³)               ………………….(2)

     From Eqn(1) and (2), we get

                        8.864*10000=D*Δ*10000

                        D=8.64*B/Δ 

EXAMPLE:

       Calculate delta based on the following data

                     Base peroid=110 days

                      Duty=1400ha/cumec

                      Delta=?

            solution,

            Δ =8.64*110/1400

             Δ=0.68m

             Δ =68cm

  

 

                       

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