The area of land that can be irrigated with a unit volume of water supplied is called duty. It is denoted by D.
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 *A*10000(m³) ………………….(2)
From Eqn(1) and (2), we get
Calculate delta based on the following data
Base peroid=110 days