Unit which is constituted from heads making irrigation in irrigation area is called as operating unit. Maximum operating unit is calculated by means of following formula.
Nmax=(Tg/Ta)*SA (15)
Minimum operating unit is also calculated by means of following formula.
Nmin=Zq/Q (16)
Where.
q:sprinkler flow m3/h Q:system flow m3/h
Nmax: maximum number of station Tg: achievable irrigation duration per day, h/ day Ta: irrigation duration, h SA: irrigation interval, day.
Operation unit is considered a number between Nmin and Nmax in planning step.
5.3 Hydraulic calculation
Two different head loss are occurred in duration of water’s reaching from resource to plant in delivery of water in an irrigation system. One of them is friction head loss. Friction head loss occurs due to friction within pipes and it is related to length, dimension and coefficient of roughness of pipes. Friction losses are calculated by means of formula of Darcy-Weisbach below.
hf=A(L/D)(v2/2g) (17)
Where.
hf:friction head loss m A:friction coefficient L: length of line (m)
D:Inner diameter of pipe work (m) v: velocity of fluid (m/s) g: acceleration due to gravity (m/s2)
Second local head losses occurring in system is called as geodetic and changes depending on type of equipment used. Local head losses are calculated by means of formula below.
hl: kf*V2/2g (18)
Where.
hl: local head losses, m
kf: friction coefficient of irrigation equipment V: velocity of fluid, m/ s g: acceleration due to gravity, m/s2
